Polymer/liquid crystal composite and liquid crystal element

ABSTRACT

The invention is generally related to a polymer/liquid crystal composite, which includes a liquid crystal material which exhibits an optically isotropic liquid crystal phase in the temperature range of approximately 5° C. or more in the elevated temperature process but does not exhibit a nematic phase; and a polymer, and which is used for an element driven in a state of the optically isotropic liquid crystal phase.

This application claims priority under 35 U.S.C. § 119 to JapanesePatent Application Nos. JP 2007-123522 (filed May 8, 2007) and2008-117127 (filed Apr. 28, 2008) each which applications is expresslyincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a liquid crystal material contained in apolymer/liquid crystal composite including the liquid crystal materialand a polymer for use in an element driven in a state of an opticallyisotropic liquid crystal phase, wherein the liquid crystal materialexhibits the optically isotropic liquid crystal phase in the temperaturerange of approximately 5° C. or more in the elevated temperature processbut does not exhibit a nematic phase; and a mixture comprising a liquidcrystal material and a monomer, the polymer/liquid crystal composite anda liquid crystal element using the composite thereof.

2. Related Art

When a nematic liquid crystal compound/composition is heated in a statewhere a nematic phase is exhibited, an isotropic phase is graduallyappeared. In such an isotropic phase in a nematic liquid crystalcompound/composition (hereinafter sometimes referred to as “non-liquidcrystalline isotropic phase”), the Kerr effect, which is a phenomenon inwhich a value of electric birefringence Δn_(E) (a value of birefringenceinduced when electric field is applied on an isotropic medium) isproportional to the square of electric field E [Δn_(E)=KλE² (K: Kerrconstant (Kerr coefficient), λ: wavelength)], is observed. Specifically,a high Kerr constant is observed at a temperature just above the nematicphase-isotropic phase transition temperature. It is thought that theKerr effect is attributed to the presence of short range order ofnematic molecular alignment generated by heat fluctuation in anon-liquid crystalline isotropic phase.

In the case of a liquid crystal material, the Kerr effect is observednot only in a non-liquid crystalline isotropic phase but also in a bluephase. A blue phase is generally exhibited between a chiral nematicphase and a non-liquid crystalline isotropic phase, and in general, thetemperature range thereof is very narrow (about approximately 1 toapproximately 2° C.).

On the other hand, in a composite material of a polymer and a chiralliquid crystal, an “optically isotropic liquid crystal phase (a phase inwhich liquid crystal molecular alignment is macroscopically isotropic,and liquid crystalline order is microscopically present)” is exhibitedin a relatively wide temperature range, and in such a phase, the Kerreffect with a high Kerr constant has been observed (for example, seeJapanese Laid-Open Patent Publication No. 2003-327966; Nature Materials,1, 64-68 (2002); Advanced Materials, 17, 96-98 (2005); and AdvancedMaterials, 17, 2311-2315 (2005)).

However, though an optically isotropic liquid crystal phase is exhibitedin a wide temperature range in the case of such a composite material,there is a problem that birefringence may remain even if returning to aliquid crystalline state, in which electric field is not applied, afterapplication of high electric field. Therefore, in the case of liquidcrystal elements such as indicating element, use of a composite materialwith a polymer is limited.

SUMMARY OF THE INVENTION

Under the above-described circumstances, a polymer/liquid crystalcomposite, in which birefringence does not remain even if returning to aliquid crystalline state, in which electric field is not applied, afterapplication of high electric field, is desired. A liquid crystalmaterial with excellent long-term reliability is desired.

It has been observed that a liquid crystal material, which exhibits anoptically isotropic liquid crystal phase (e.g., a blue phase) in a widetemperature range in the elevated temperature process but does notexhibit a nematic phase, can be obtained when chiral dopants are addedto a liquid crystal composition, wherein the difference between theupper limit and the lower limit of a temperature allowing coexistence ofthe nematic phase and a non-liquid crystalline isotropic phase or thedifference between the upper limit and the lower limit of a temperatureallowing coexistence of a chiral nematic phase and the non-liquidcrystalline isotropic phase has a predetermined value, and wherein theoptically isotropic liquid crystal phase is not exhibited in theelevated temperature process.

The invention includes:

[1] A liquid crystal material contained in a polymer/liquid crystalcomposite including the liquid crystal material and a polymer for use inan element driven in a state of an optically isotropic liquid crystalphase, wherein the liquid crystal material exhibits the opticallyisotropic liquid crystal phase in the temperature range of approximately4.8° C. or more in the elevated temperature process but does not exhibita nematic phase.

[2] The liquid crystal material according to item [1], wherein theliquid crystal material is a composition includes a liquid crystalcomposition A, wherein the difference between the upper limit and thelower limit of a temperature allowing coexistence of the nematic phaseand a non-liquid crystalline isotropic phase or the difference betweenthe upper limit and the lower limit of a temperature allowingcoexistence of a chiral nematic phase and the non-liquid crystallineisotropic phase is approximately 3.0° C. to approximately 150° C., andwherein the optically isotropic liquid crystal phase is not exhibited inthe elevated temperature process, and chiral dopants.

[3] The liquid crystal material according to item [1], wherein theliquid crystal material is a composition includes a liquid crystalcomposition A, wherein the difference between the upper limit and thelower limit of a temperature allowing coexistence of the nematic phaseand a non-liquid crystalline isotropic phase or the difference betweenthe upper limit and the lower limit of a temperature allowingcoexistence of a chiral nematic phase and the non-liquid crystallineisotropic phase is approximately 6.0° C. to approximately 150° C., andwherein the optically isotropic liquid crystal phase is not exhibited inthe elevated temperature process, and chiral dopants.

[4] The liquid crystal material according to any one of items [1]-[3],wherein the liquid crystal material is the liquid crystal composition Bincluding the liquid crystal composition A, which does not exhibit theoptically isotropic liquid crystal phase in the elevated temperatureprocess, and the chiral dopants, and wherein the liquid crystalcomposition A includes approximately 5 to approximately 80 wt % ofcomponent 1 having the clearing point T₁ and approximately 20 toapproximately 95 wt % of component 2 having the clearing point T₂, andthe clearing point T₁, the clearing point T₂ and the clearing point T×Bof the liquid crystal composition B satisfy the following conditions:T₁>T₂T ₁ −T×B≧100° C.

[5] The liquid crystal material according to any one of items [1]-[3],wherein the liquid crystal material is the liquid crystal composition Bincluding the liquid crystal composition A, which does not exhibit theoptically isotropic liquid crystal phase in the elevated temperatureprocess, and the chiral dopants, and wherein the liquid crystalcomposition A includes approximately 5 to approximately 70 wt % ofcomponent 1 having the clearing point T₁ and approximately 30 toapproximately 95 wt % of component 2 having the clearing point T₂, andthe clearing point T₁, the clearing point T₂ and the clearing point T×Bof the liquid crystal composition B satisfy the following conditions:T₁>T₂T ₁ −T×B≧150° C.

[6] The liquid crystal material according to any one of items [1]-[3],wherein the liquid crystal material is the liquid crystal composition Bincluding the liquid crystal composition A, which does not exhibit theoptically isotropic liquid crystal phase in the elevated temperatureprocess, and the chiral dopants, and wherein the liquid crystalcomposition A includes approximately 5 to approximately 70 wt % ofcomponent 1 having the clearing point T₁ and approximately 30 toapproximately 95 wt % of component 2 having the clearing point T₂, andthe clearing point T₁, the clearing point T₂ and the clearing point T×Bof the liquid crystal composition B satisfy the following conditions:T₁>T₂T ₁ −T×B≧200° C.

[7] The liquid crystal material according to any one of items [1]-[3],wherein the liquid crystal material is the liquid crystal composition Bincluding the liquid crystal composition A, which does not exhibit theoptically isotropic liquid crystal phase in the elevated temperatureprocess, and the chiral dopants, and wherein the liquid crystalcomposition A includes approximately 5 to approximately 80 wt % ofcomponent 1 having the clearing point T₁ and approximately 20 toapproximately 95 wt % of component 2 having the clearing point T₂, andthe clearing point T₁, the clearing point T₂ and the clearing point T×aof a liquid crystal composition a, in which all the chiral dopants areexcluded from the liquid crystal composition A satisfy the followingconditions:T₁>T₂T ₁ −T×a≧100° C.

[8] The liquid crystal material according to any one of items [4]-[7],wherein the component 1 includes a liquid crystal compound having theclearing point of approximately 150° C. or higher and the component 2includes a liquid crystal compound having the clearing point ofapproximately 47° C. or lower.

The component 1 preferably includes a liquid crystal compound having theclearing point of approximately 200° C. or higher, more preferablyincludes a liquid crystal compound having the clearing point ofapproximately 220° C. or higher, and particularly preferably consists ofa liquid crystal compound having the clearing point of approximately250° C. or higher.

The component 2 preferably includes a liquid crystal compound having theclearing point of approximately 25° C. or lower, and particularlypreferably includes a liquid crystal compound having the clearing pointof approximately 0° C. or lower.

[9] The liquid crystal material according to any one of items [4]-[8],wherein the component 1 includes a compound represented by the followinggeneral formula (1):

wherein:

-   R¹ is hydrogen or alkyl having 1 to 20 carbon atoms, wherein any    —CH₂— in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—,    —CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl and an    alkyl in which any —CH₂— is substituted with —O—, —S—, —COO—, —OCO—,    —CH═CH—, —CF═CF— or —C≡C— can be substituted with halogen;-   R² is hydrogen, halogen, —CN, —N═C═O, —N═C═S, —CF₃, —OCF₃ or alkyl    having 1 to 20 carbon atoms, wherein any —CH₂— in the alkyl can be    substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—, —CF═CF— or —C≡C—,    and any hydrogen in the alkyl and an alkyl in which any —CH₂— is    substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—, —CF═CF— or —C≡C—    can be substituted with halogen, and —CH₃ in these alkyls can be    substituted with —CN;-   A¹ to A⁵ are each independently an aromatic or nonaromatic 3- to    8-membered ring or a condensed ring having 9 or more carbon atoms,    wherein: any hydrogen in these rings can be substituted with    halogen, alkyl having 1 to 3 carbon atoms or alkyl halide; —CH₂— in    the rings can be substituted with —O—, —S—, or —NH—; —CH═ can be    substituted with —N═; and A¹ to A⁵ are not tetrahydropyran rings;-   Z¹ to Z⁴ are each independently a single bond or alkylene having 1    to 8 carbon atoms, wherein any —CH₂— in the alkylene can be    substituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —N═N—,    —CH═N—, —N═CH—, —N(O)═N—, —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C—, and    any hydrogen in the alkylene and an alkylene in which any —CH₂— is    substituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —N═N—,    —CH═N—, —N═CH—, —N(O)═N—, —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C— can be    substituted with halogen; and-   n¹ to n³ are each independently 0 or 1; when R² is hydrogen or    fluorine, n² and n³ are 1; when at least one of Z¹ to Z⁴ is —CF₂O—,    n² and n³ are 1; when Z⁴ is —COO—, n² and n³ are 1; and only when at    least one of A⁴ and A⁵ is a condensed ring having 9 or more carbon    atoms, all of n¹ to n³ can be 0.

[10] The liquid crystal material according to item [9], wherein:

-   R¹ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂— in the    alkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH— or    —C≡C—;-   R² is halogen, —CN, —N═C═O, —N═C═S, —CF₃, —OCF₃ or alkyl having 1 to    20 carbon atoms, wherein any —CH₂— in the alkyl can be substituted    with —O—, —CH═CH— or —C≡C—, and any hydrogen in the alkyl and an    alkyl in which any —CH₂— is substituted with —O—, —CH═CH— or —C≡C—    can be substituted with halogen, and —CH₃ in these alkyls can be    substituted with —CN;-   A¹ to A⁵ are each independently a benzene ring, a naphthalene ring    or a cyclohexane ring, wherein any hydrogen in these rings can be    substituted with halogen, alkyl having 1 to 3 carbon atoms or alkyl    halide, and —CH₂— in the rings can be substituted with —O— or —S—,    and —CH═ can be substituted with —N═; and-   Z¹ to Z⁴ are each independently a single bond or alkylene having 1    to 4 carbon atoms, wherein any —CH₂— in the alkylene can be    substituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —CH═CH—,    —CF═CF— or —C≡C—, and any hydrogen in the alkylene and an alkylene    in which any —CH₂— is substituted with —O—, —S—, —COO—, —OCO—,    —CSO—, —OCS—, —CH═CH—, —CF═CF— or —C≡C— can be substituted with    halogen.

[11] The liquid crystal material according to item [9], wherein:

-   R¹ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂—    nonadjacent to the aromatic ring in the alkyl can be substituted    with —CH═CH—, and any —CH₂— in the alkyl or alkenyl can be    substituted with —O—;-   R² is fluorine, chlorine, —CN, —N═C═S or alkyl having 1 to 20 carbon    atoms, wherein any —CH₂— in the alkyl can be substituted with —O—,    —CH═CH— or —C≡C—, and any hydrogen in the alkyl and an alkyl in    which any —CH₂— is substituted with —O—, —CH═CH— or —C≡C— can be    substituted with halogen;-   A¹ to A⁵ are each independently a benzene ring, a naphthalene ring    or a cyclohexane ring, wherein any hydrogen in the rings can be    substituted with fluorine or chlorine, and —CH₂— can be substituted    with —O— or —S—, and —CH═ can be substituted with —N═; and-   Z¹ to Z⁴ are each independently a single bond, —CF₂O— or —C≡C—.

[12] The liquid crystal material according to item [9], wherein:

-   R¹ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂—    nonadjacent to the aromatic ring in the alkyl can be substituted    with —CH═CH—, and any —CH₂— in the alkyl or alkenyl can be    substituted with —O—;-   R² is fluorine, chlorine, —CN or alkyl having 1 to 10 carbon atoms,    wherein any —CH₂— in the alkyl can be substituted with —O—, and any    hydrogen in the alkyl and an alkyl in which any —CH₂— is substituted    with —O— can be substituted with halogen;-   A¹ to A⁵ are each independently a benzene ring, a dioxane ring or a    cyclohexane ring, wherein any hydrogen in the benzene ring can be    substituted with fluorine or chlorine;-   Z¹ to Z⁴ are each independently a single bond or —C≡C—; and-   n¹ is 1, and n² and n³ are 0.

[13] The liquid crystal material according to any one of items [4]-[12],wherein the component 2 includes a compound represented by the followinggeneral formula (2):

wherein:

-   R³ is hydrogen or alkyl having 1 to 20 carbon atoms, wherein any    —CH₂— in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—,    —CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl and an    alkyl in which any —CH₂— is substituted with —O—, —S—, —COO—, —OCO—,    —CH═CH—, —CF═CF— or —C≡C— can be substituted with halogen;-   R⁴ is halogen, —CN, —N═C═O, —N═C═S, —CF₃, —OCF₃, —C≡C—CN, —C═C—CF₃    or —C≡C—CF₃;-   A⁶, A⁷ and A⁸ are each independently an aromatic or nonaromatic 3-    to 8-membered ring or a condensed ring having 9 or more carbon    atoms, wherein any hydrogen in these rings can be substituted with    halogen, alkyl having 1 to 3 carbon atoms or alkyl halide; any —CH₂—    in the rings can be substituted with —O—, —S—, or —NH—; and —CH═ can    be substituted with —N═;-   Z⁶ and Z⁷ are a single bond or alkylene having 1 to 8 carbon atoms,    wherein any —CH₂— in the alkylene can be substituted with —O—, —S—,    —COO—, —OCO—, —CSO—, —OCS—, —N═N—, —CH═N—, —N═CH—, —N(O)═N—,    —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the    alkylene and an alkylene in which any —CH₂— is substituted with —O—,    —S—, —COO—, —OCO—, —CSO—, —OCS—, —N═N—, —CH═N—, —N═CH—, —N(O)═N—,    —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C— can be substituted with halogen;    and-   n⁶ and n⁷ are 0 or 1, wherein both n⁶ and n⁷ are 1 only when at    least one of Z⁶ and Z⁷ is —CF₂O—, and n⁶ and n⁷ are 0 when A⁷ or A⁸    is a condensed ring having 9 or more carbon atoms.

[14] The liquid crystal material according to item [13], wherein:

-   R³ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂— in the    alkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH— or    —C≡C—;-   R⁴ is halogen, —CN, —N═C═S, —CF₃, —C≡C—CN or —C≡C—CF₃;-   A⁶, A⁷ and A⁸ are each independently a benzene ring, a naphthalene    ring or a cyclohexane ring, wherein any hydrogen in these rings can    be substituted with halogen; any —CH₂— in the rings can be    substituted with —O— or —S—; and —CH═ can be substituted with —N═;    and-   Z⁶ and Z⁷ are a single bond or alkylene having 1 to 4 carbon atoms,    wherein any —CH₂— in the alkylene can be substituted with —O—, —S—,    —COO—, —OCO—, —CSO—, —OCS—, —CH═CH—, —CF═CF— or —C≡C—; and any    hydrogen in the alkylene and an alkylene in which any —CH₂— is    substituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —CH═CH—,    —CF═CF— or —C≡C— can be substituted with halogen.

[15] The liquid crystal material according to item [13], wherein:

-   R³ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂—    nonadjacent to the aromatic ring in the alkyl can be substituted    with —CH═CH—;-   R⁴ is halogen, —CN, —N═C═S, —CF₃, —OCF₃, —C≡C—CN, —CH═CH—CF₃ or    —C≡C—CF₃;-   A⁶, A⁷ and A⁸ are each independently a benzene ring, a naphthalene    ring or a cyclohexane ring, wherein any hydrogen in these rings can    be substituted with fluorine or chlorine; any —CH₂— in these rings    can be substituted with —O—; and —CH═ can be substituted with —N═;    and-   Z⁶ and Z⁷ are each independently a single bond, —COO—, —CF₂O— or    —C≡C—.

[16] The liquid crystal material according to item [13], wherein:

-   R³ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂—    nonadjacent to the aromatic ring in the alkyl can be substituted    with —CH═CH—;-   R⁴ is halogen or —CN;-   A⁷ and A⁸ are each independently a benzene ring, a dioxane ring or a    cyclohexane ring, wherein any hydrogen in the benzene ring can be    substituted with fluorine;-   Z⁷ is a single bond or —COO—; and-   n⁶ is 0 and n⁷ is 0 or 1.

[17] The liquid crystal material according to any one of items [4]-[12],wherein the component 2 consists of a compound represented by thefollowing general formula (3):

wherein:

-   R⁵ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂— in the    alkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—,    —CF═CF— or —C≡C—; and any hydrogen in the alkyl can be substituted    with halogen;-   X^(a) is fluorine, chlorine, —CN, —N═C═S, —CF₃, —OCF₃, —C≡C—CN,    —CH═CH—CF₃ or —C≡C—CF₃;-   Z¹² is a single bond, —COO—, —CF₂O— or —C≡C—; and-   L⁸ to L¹¹ are each independently hydrogen or fluorine.

[18] The liquid crystal material according to item [17], wherein:

-   R⁵ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂—    nonadjacent to the aromatic ring in the alkyl can be substituted    with —CH═CH—;-   X^(a) is fluorine or —CN;-   Z¹² is —COO—; and-   L⁸ to L¹¹ are each independently hydrogen or fluorine, wherein at    least two of them are fluorine.

[19] The liquid crystal material according to any one of items [4]-[12],wherein the component 2 consists of a compound represented by thefollowing general formula (4):

wherein:

-   R⁶ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂— in the    alkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—,    —CF═CF— or —C≡C—; and any hydrogen in the alkyl can be substituted    with halogen;-   X^(b) is fluorine, chlorine, —CF₃, —OCF₃, —C═C—CF₃ or —C≡C—CF₃;-   Z¹³ and Z¹⁴ are each independently a single bond or —CF₂O—, wherein    at least one of them is —CF₂O—; and-   L¹² to L¹⁷ are each independently hydrogen, fluorine or chlorine.

[20] The liquid crystal material according to item [19], wherein:

-   R⁶ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂—    nonadjacent to the aromatic ring in the alkyl can be substituted    with —CH═CH—;-   X^(b) is fluorine, chlorine, —CF₃, —OCF₃ or —C═C—CF₃;-   Z¹³ is a single bond and Z¹⁴ is —CF₂O—; and-   L¹² to L¹⁷ are each independently hydrogen or fluorine, wherein at    least two of them are fluorine.

[21] The liquid crystal material according to any one of items [2]-[20],wherein the chiral dopants included in the liquid crystal materialinclude one or more compounds represented by any one of the followingformulae (K1) to (K5):

wherein:

-   each R^(K) is independently hydrogen, halogen, —CN, —N═C═O, —N═C═S    or alkyl having 1 to 20 carbon atoms, wherein any —CH₂— in the alkyl    can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—, —CF═CF— or    —C≡C—; and any hydrogen in the alkyl can be substituted with    halogen;-   each A is independently an aromatic or nonaromatic 3- to 8-membered    ring or a condensed ring having 9 or more carbon atoms, wherein any    hydrogen in these rings can be substituted with halogen, alkyl    having 1 to 3 carbon atoms or haloalkyl; —CH₂— in the rings can be    substituted with —O—, —S— or —NH—; and —CH═ can be substituted with    —N═;-   each Z is independently a single bond or alkylene having 1 to 8    carbon atoms, wherein any —CH₂— can be substituted with —O—, —S—,    —COO—, —OCO—, —CSO—, —OCS—, —N═N—, —CH═N—, —N═CH—, —N(O)═N—,    —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C—; and any hydrogen can be    substituted with halogen;-   X is a single bond, —COO—, —OCO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or    —CH₂CH₂—; and-   m is 1 to 4.

[22] The liquid crystal material according to any one of items [2]-[20],wherein the chiral dopants included in the liquid crystal materialincludes one or more compounds represented by any one of the followingformulae (K2-1) to (K2-8) and (K5-1) to (K5-3):

wherein:

-   each R^(K) is independently alkyl having 3 to 10 carbon atoms,    wherein —CH₂— adjacent to the ring in the alkyl can be substituted    with —O—; and any —CH₂— can be substituted with —CH═CH—.

[23] The liquid crystal material according to any one of items [2]-[22],wherein the chiral dopants are included in an amount of approximately 1to approximately 40 wt % per the weight of the liquid crystalcomposition B.

[24] A mixture including the liquid crystal material according to anyone of items [1]-[23] and a polymerizable monomer.

[25] The mixture according to item [24], wherein the polymerizablemonomer is a photopolymerizable monomer or a thermopolymerizablemonomer.

[26] A polymer/liquid crystal composite for use in an element driven ina state of an optically isotropic liquid crystal phase, which can beobtained by polymerizing the mixture according to item [24] or [25].

[27] The polymer/liquid crystal composite according to item [26],wherein the mixture is obtained by polymerization in a state of anoptically isotropic liquid crystal phase or an isotropic phase.

[28] The polymer/liquid crystal composite according to item [27],wherein a polymer included in the polymer/liquid crystal composite has amesogenic moiety.

[29] The polymer/liquid crystal composite according to any one of items[26]-[28], wherein the polymer included in the polymer/liquid crystalcomposite has a cross-linked structure.

[30] The polymer/liquid crystal composite according to any one of items[26]-[29], including the liquid crystal material in an amount ofapproximately 60 to approximately 99 wt % and the polymer in an amountof approximately 1 to approximately 40 wt %.

[31] The polymer/liquid crystal composite according to any one of items[26]-[30], wherein the pitch is approximately 700 nm or lower.

[32] A liquid crystal element, in which an electrode is placed on one orboth surfaces thereof, and which has a polymer/liquid crystal compositeplaced between substrates and an electric field applying means forapplying electric field on the polymer/liquid crystal composite via theelectrode, wherein the polymer/liquid crystal composite is thataccording to any one of items [26]-[31].

[33] A liquid crystal element, in which an electrode is placed on one orboth surfaces thereof, and which has a pair of substrates, at least oneof which is transparent; a polymer/liquid crystal composite placedbetween the substrates; and polarization plates placed on the externalsides of the substrates, and which has an electric field applying meansfor applying electric field on the polymer/liquid crystal composite viathe electrode, wherein the polymer/liquid crystal composite is thepolymer/liquid crystal composite according to any one of items[26]-[31].

[34] The liquid crystal element according to item [32] or [33], whereinthe electrode is constituted on at least one of the pair of substratesso that electric field can be applied in at least two directions.

[35] The liquid crystal element according to item [32] or [33], whereinthe electrode is constituted on one or both of the pair of substratesplaced in parallel with each other so that electric field can be appliedin at least two directions.

[36] The liquid crystal element according to any one of items [32]-[35],wherein the electrode is placed in a matrix state to constitute a pixelelectrode; each pixel has an active element; and the active element is athin film transistor (TFT).

The “polymer/liquid crystal composite” in the invention is notparticularly limited as long as it is a composite material comprisingboth a liquid crystal material and a polymer compound, but a polymer maybe phase-separated from the liquid crystal material in a state where apart or all of the polymer is not dissolved in the liquid crystalmaterial. The term “nematic phase” as used herein means anarrowly-defined nematic phase in which no chiral nematic phase isincluded, unless otherwise specified.

In the polymer/liquid crystal composite related to the preferredembodiment of the present invention, an optically isotropic liquidcrystal phase can be exhibited in a wide temperature range. Further, inthe polymer/liquid crystal composite related to the preferred embodimentof the present invention, remaining birefringence after electric fieldelimination can be reduced. The response speed of the polymer/liquidcrystal composite related to the preferred embodiment of the presentinvention is very fast. The polymer/liquid crystal composite related tothe preferred embodiment of the present invention can be suitably usedfor a liquid crystal elements and the like such as indicating elementbased on these effects.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 shows polarization microscope images of liquid crystalcomposition A-2 in the lowered temperature process;

FIG. 2 shows a comb-like electrode substrate used in Example 1; and

FIG. 3 shows an optical system used in Examples 2, 3 and 4.

DETAILED DESCRIPTION OF THE INVENTION

The liquid crystal material of the invention is a liquid crystalmaterial used for a polymer/liquid crystal composite comprising theliquid crystal material and a polymer for use in an element driven in astate of an optically isotropic liquid crystal phase, wherein the liquidcrystal material exhibits the optically isotropic liquid crystal phasein the temperature range of approximately 4.8° C. or more in theelevated temperature process but does not exhibit a nematic phase.

A liquid crystal compound/composition, which exhibits a nematic phase(except a chiral nematic phase), does not exhibit an optically isotropicliquid crystal phase at any temperature. Therefore, the compositematerial of the invention and the liquid crystal material contained inthe composite material do not exhibit the nematic phase at anytemperature.

Further, a nematic phase and a chiral nematic phase are not an opticallyisotropic liquid crystal phase. Therefore, the composite material of thepresent invention used in an element driven in the state of theoptically isotropic liquid crystal phase cannot be used in an elementdriven in the state of the nematic phase or chiral nematic phase.

The polymer/liquid crystal composite of the invention is an opticallyisotropic polymer/liquid crystal composite used in an element driven ina state of an optically isotropic liquid crystal phase. That is, thepolymer/liquid crystal composite of the invention is a compositematerial which can be used in a liquid crystal element in a liquidcrystalline state (such as a blue phase) showing optically isotropicproperties.

1. Liquid Crystal Material

The liquid crystal material contained in the composite material of theinvention is not particularly limited, but exhibits the opticallyisotropic liquid crystal phase in the temperature range of approximately4.8° C. or more in the elevated temperature process and does not exhibitthe nematic phase.

Positive/negative of the dielectric anisotropy of liquid crystalcomposition a (a composition obtained by excluding all chiral dopantsfrom liquid crystal composition A) contained in the composite materialof the invention is not particularly limited, but the dielectricanisotropy of liquid crystal composition a is preferably positive. Withrespect to the absolute value of the value of dielectric anisotropy ofthe liquid crystal material (Δ∈) and the value of optical anisotropyanisotropy (Δn), the higher these values, the higher the electricbirefringence, and therefore these values are preferably as high aspossible.

The polymer/liquid crystal composite of the invention preferably showsthe Kerr constant of 1×10⁻¹¹ mV⁻² or higher in order to achieve a lowdrive voltage, and more preferably shows the Kerr constant of 1×10⁻⁸mV⁻² or higher.

Preferably in the composite material of the invention, there is a regionwhere the ratio of values of the Kerr constant in the temperaturedifference of approximately 10° C. is 1.5 or lower, that is, theelectric birefringence ratio preferably has low dependency ontemperature and is stable in a wide temperature range.

The absolute value of the product of optical anisotropy anisotropy (Δn)and dielectric anisotropy (Δ∈) in the liquid crystal composition acontained in the composite material of the invention is preferablyapproximately 0.5 to approximately 60, more preferably approximately 2to approximately 60, and even more preferably approximately 5 toapproximately 60 particularly when using in an indicating element. Theaforementioned product can be increased by increasing Δn, or Δ∈, or bothof them. In general, by increasing the product, Δn_(E) is increased andthe drive voltage is decreased.

Moreover, since the pitch has a close relationship with the coherencelength, the pitch is preferably optimized depending on purposes in viewof the ratio of mixed polymer, the ratio of added chiral dopants, HTP ofchiral dopants and the like. The coherence length is preferablyapproximately 10 to approximately 800 nm. Since the Kerr constant isproportional to the square of the coherence length, the coherence lengthis preferably as long as possible within a range in which the opticallyisotropic liquid crystal phase can be obtained.

In the liquid crystal material contained in the composite material ofthe invention, a liquid crystal compound having no optical activity canbe used together with chiral dopants. The viscosity of the liquidcrystal compound is correlated to response time of refractive-indexchange. When high-speed response is required, a liquid crystal compoundhaving low viscosity is preferred. Therefore, the viscosity of theliquid crystal compound having no optical activity to be used with thechiral dopants are preferably approximately 1000 mPa·s or lower, morepreferably approximately 400 mPa·s or lower, and particularly preferablyapproximately 200 mPa·s or lower.

In general, when the weight ratio between the chiral dopants and theliquid crystal compound having no optical activity, which constitute theliquid crystal material of the invention, is within the range fromapproximately 1:99 to approximately 40:60, a composite material, whichhas an enough viscosity to function in a liquid crystal element, andwhich exhibits an optically isotropic liquid crystal phase, can beprovided.

Examples of liquid crystal compounds to be used in the polymer/liquidcrystal composite of the invention include a compound represented byformula (1), a compound represented by formula (2), a compoundrepresented by formula (3) and a compound represented by formula (4).

Further, examples of liquid crystal materials to be used in thepolymer/liquid crystal composite of the invention include liquid crystalcomposition B exhibiting an optically isotropic liquid crystal phase,which can be obtained by adding a predetermined amount of chiral dopantsto liquid crystal composition A, which is obtained by mixing thecompound represented by formula (1) with the compound represented byformula (2), (3), (4) etc. The liquid crystal composition A may includechiral dopants within a range where the optically isotropic liquidcrystal phase is not exhibited.

In the liquid crystal composition A of the invention, the component 1preferably consists of one compound represented by formula (1) or aplurality of compounds represented by formula (1), but such compoundsare not limited to those represented by formula (1) as long as they havea high clearing point. Similarly, the component 2 preferably consists ofone compound represented by formula (2), (3) or (4) or a plurality ofcompounds represented by formula (2), (3) or (4), but such compounds arenot limited to those represented by formula (2), (3) or (4) as long asthey have a low clearing point.

The “liquid crystal composition” as used herein refers to a compositionhaving a liquid crystal phase or a composition in which a materialhaving a liquid crystal phase is mixed, wherein the liquid crystalphase-non-liquid crystalline isotropic phase transition temperature isnot significantly reduced.

When the liquid crystal compound or the liquid crystal composition doesnot exhibit the liquid crystal phase, a method for calculating a liquidcrystal phase-non-liquid crystalline isotropic phase transition pointusing an extrapolation method is employed as described below. Thisextrapolation method can be applied to a compound or a composition whoseliquid crystal phase-non-liquid crystalline isotropic phase transitionpoint is higher than the decomposition temperature of liquid crystal.

1.1 Liquid Crystal Composition A

The liquid crystal composition A is a composition, wherein thedifference between the upper limit and the lower limit of a temperatureallowing coexistence of the nematic phase and the non-liquid crystallineisotropic phase or the difference between the upper limit and the lowerlimit of a temperature allowing coexistence of the chiral nematic phaseand the non-liquid crystalline isotropic phase is approximately 3.0° C.or more, and wherein the optically isotropic liquid crystal phase is notexhibited in the elevated temperature process.

The liquid crystal composition A is not particularly limited as long asit has the above-described characteristics, and the chiral dopants mayor may not be contained therein.

1.1.1. Clearing Point

In the liquid crystal composition A of the invention, the clearingpoints (T₁) and (T₂) of the components 1 and 2 contained in the liquidcrystal composition A and the clearing point (T×B) of the liquid crystalcomposition B as described later preferably satisfy the followingformulae:T₁>T₂T ₁ −T×B≧100° C.

More preferably, these clearing points satisfy the following formulae:T₁>T₂T ₁ −T×B≧150° C.

Particularly preferably, these clearing points satisfy the followingformulae:T₁>T₂T ₁ −T×B≧200° C.

When each of the component 1 and the component 2 includes a plurality ofcompounds, the clearing points of the component 1 and the component 2are clearing points of compositions, each of which is obtained based onthe weight ratio of compounds constituting the component 1 or thecomponent 2.

The liquid crystal composition A having the clearing point T×A can beprepared by selecting the component 1, which includes a compound(compounds) having a high clearing point, and the component 2, whichincludes a compound (compounds) having a low clearing point, andaccording to circumstances, by adding a component which does notcorrespond to the component 1 or 2 (third component) and chiral dopantsin view of other property parameters such as Δn and Δ∈.

For example, when the liquid crystal composition A includes 5 compoundsA1 to A5, and they are listed as compounds A1, A2, A3, A4 and A5 indescending order of clearing point, at least the compound A1 having thehighest clearing point corresponds to the component 1, and the compoundA5 having the lowest clearing point corresponds to the compoundcontained in the component 2. Moreover, the compound A2 having thesecond highest clearing point may be optionally contained in thecomponent 1, and the compound A4 having the second lowest clearing pointmay be contained in the component 2. Furthermore, since there may be acompound which does not correspond to the component 1 or 2, for example,when the compound A1 and the compound A2 correspond to the compoundscontained in the component 1, and the compound A4 and the compound A5correspond to the compounds contained in the component 2, the compoundA3 is the third component which does not correspond to the component 1or 2.

That is, whether or not each compound contained in the liquid crystalcomposition A corresponds to the component 1 or 2 is not particularlylimited. It is preferable that, when compounds contained in the liquidcrystal composition A are divided between the component 1 having arelatively high clearing point and the component 2 having a relativelylow clearing point, the clearing points of the components 1 and 2 andthe liquid crystal composition satisfy the above-described formulae.

When the liquid crystal composition A comprises chiral dopants, theliquid crystal composition can be divided into a liquid crystalcomposition a, which does not include the chiral dopants, and the chiraldopants. In general, the clearing point of the liquid crystalcomposition a (T×a) is higher than the clearing point of the liquidcrystal composition A (T×A), and the clearing point of the liquidcrystal composition A (T×A) is higher than the clearing point of theliquid crystal composition B (T×B). In this case, preferably T₁, T₂ andT×a satisfy the following formulae:T₁>T₂T ₁ −T×a≧100° C.

More preferably, these clearing points satisfy the following formulae:T₁>T₂T ₁ −T×a≧150° C.

Particularly preferably, these clearing points satisfy the followingformulae:T₁>T₂T ₁ −T×a≧200° C.

The method for calculating the clearing point is as follows. When thecomposition ratio (by weight) of compound A1: compound A2: compound A3:compound A4: compound A5 is C1:C2:C3:C4:C5, and the component 1 includesthe compound A1 and the compound A2 and the component 2 includes thecompound A4 and the compound A5, T₁ is a clearing point in a mixture inwhich the compound A1 and the compound A2 are mixed in the ratio (byweight) of C1:C2 and T₂ is a clearing point in a mixture in which thecompound A4 and the compound A5 are mixed in the ratio (by weight) ofC4:C5.

The clearing point means a point at which a compound or compositionexhibits a non-liquid crystalline isotropic phase in the elevatedtemperature process. Specific examples of clearing points include N-Ipoint, which is a phase transition point from a nematic phase to anon-liquid crystalline isotropic phase. In the case of the liquidcrystal composition of the invention, a coexisting state of a non-liquidcrystalline isotropic phase and a liquid crystal phase may be exhibited.In this case, a temperature at which a non-liquid crystalline isotropicphase is initially appeared in the elevated temperature process isdefined as a clearing point. Further, a clearing point of a compoundwhich does not exhibit a liquid crystal phase, i.e., a compound havingK-I point, is K-I point or lower. According to need, the method forcalculating a liquid crystal phase-non-liquid crystalline isotropicphase transition point using the extrapolation method as described belowcan be employed.

1.1.2. Component 1

The component 1 preferably includes a compound having a relatively highclearing point. Specifically, the component 1 preferably includes acompound represented by formula (1). In formula (1): R¹ is hydrogen oralkyl having 1 to 20 carbon atoms; any —CH₂— in the alkyl can besubstituted with —O—, —S—, —COO—, —OCO—, —CH═CH—, —CF═CF— or —C≡C—; andany hydrogen in the alkyl group can be substituted with halogen. Amongthem, R¹ is preferably alkyl having 1 to 10 carbon atoms, and any —CH₂—in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH— or—C≡C—. More preferably, R¹ is alkyl having 1 to 10 carbon atoms, and any—CH₂— in the alkyl can be substituted with —CH═CH— or —C≡C—. Among them,R¹ is most preferably alkyl having 1 to 10 carbon atoms or alkoxy.

In formula (1): R² is hydrogen, halogen, —CN, —N═C═O, —N═C═S, —CF₃,—OCF₃ or alkyl having 1 to 20 carbon atoms; any —CH₂— in the alkyl canbe substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—, —CF═CF— or —C≡C—;any hydrogen in the alkyl can be substituted with halogen; and —CH₃ inthe alkyl can be substituted with —CN. Among them, R² is preferablyhalogen, —CN, —N═C═O, —N═C═S, —CF₃, —OCF₃ or alkyl having 1 to 20 carbonatoms; any —CH₂— in the alkyl can be substituted with —O—, —CH═CH— or—C≡C—; any hydrogen in the alkyl can be substituted with halogen; and—CH₃ in the alkyl can be substituted with —CN. R² is more preferablyfluorine, chlorine, —CN, —N═C═S or alkyl having 1 to 20 carbon atoms,and any —CH₂— in the alkyl can be substituted with —O—, —CH═CH— or—C≡C—.

In formula (1), A¹ to A⁵ are each independently an aromatic ornonaromatic 3- to 8-membered ring or a condensed ring having 9 or morecarbon atoms, wherein any hydrogen in these rings can be substitutedwith halogen, alkyl having 1 to 3 carbon atoms or alkyl halide; —CH₂— inthe rings can be substituted with —O—, —S— or —NH—; —CH═ can besubstituted with —N═; and A¹ to A⁵ are not tetrahydropyran rings. Amongthem, preferably, A¹ to A⁵ are each independently a benzene ring, anaphthalene ring, a dioxane ring or a cyclohexane ring, wherein anyhydrogen in these rings can be substituted with halogen, alkyl having 1to 3 carbon atoms or alkyl halide, and —CH₂— in the rings can besubstituted with —O— or —S—, and —CH═ can be substituted with —N═. Morepreferably, A¹ to A⁵ are each independently a benzene ring, anaphthalene ring, a dioxane ring or a cyclohexane ring, wherein anyhydrogen in the benzene ring or the naphthalene ring can be substitutedwith fluorine, chlorine, methyl or methyl halide; —CH₂— can besubstituted with —O— or —S—; and —CH═ can be substituted with —N═. Amongthem, most preferably, A¹ to A⁵ are each independently a benzene ring, apyrimidine ring, a dioxane ring or a cyclohexane ring, wherein anyhydrogen in the benzene ring can be substituted with fluorine.

In formula (1), Z¹ to Z⁴ are each independently a single bond oralkylene having 1 to 8 carbon atoms, wherein any —CH₂— in the alkylenecan be substituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —N═N—,—CH═N—, —N═CH—, —N(O)═N—, —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C—, and anyhydrogen can be substituted with halogen. Among them, preferably, Z¹ toZ⁴ are each independently a single bond or alkylene having 1 to 4 carbonatoms, wherein any —CH₂— in the alkylene can be substituted with —O—,—S—, —COO—, —OCO—, —CSO—, —OCS—, —CH═CH—, —CF═CF— or —C≡C—, and anyhydrogen can be substituted with halogen. More preferably, Z¹ to Z⁴ areeach independently a single bond, —COO—, —CF₂O— or —C≡C—.

In formula (1), n¹ to n³ are each independently 0 or 1, wherein: n² andn³ are 1 when R² is hydrogen or fluorine; n² and n³ are 1 when at leastone of Z¹ to Z⁴ is —CF₂O—; n² and n³ are 1 when Z⁴ is —COO—; and all ofn¹ to n³ may be 0 only when at least one of A⁴ and A⁵ is a condensedring having 9 or more carbon atoms. Among them, preferably, n¹ to n³ areeach independently 0 or 1, wherein n² and n³ are 1 when R² is hydrogenor fluorine, and all of n¹ to n³ may be 0 only when at least one of A⁴and A⁵ is a condensed ring having 9 or more carbon atoms. Among them,more preferably, n¹ to n³ are each independently 0 or 1, wherein n² andn³ are 1 when R² is hydrogen or fluorine, and all of n¹ to n³ may be 0only when at least one of A⁴ and A⁵ is a condensed ring having 9 or morecarbon atoms.

The compound represented by formula (1) preferably has a clearing pointof approximately 150° C. to approximately 400° C., and more preferablyhas a clearing point of approximately 200° C. to approximately 350° C.When the clearing point is lower than approximately 150° C., it isdisadvantageous in terms of satisfying the relation between the clearingpoint of the component 1 (T₁) and the clearing point of the liquidcrystal composition B (T×B) (T₁−T×B≧100° C.). When the clearing point ishigher than approximately 400° C., the compatibility may be decreaseddepending on other compounds to be combined therewith, and the lowerlimit of temperature of the liquid crystal phase may be raised, whereincrystal is separated out at a low temperature.

1.1.3. Component 2

The component 2 is preferably a compound having a low clearing point anda large value of dielectric anisotropy. Specifically, the component 2preferably consists of a compound represented by formula (2), (3) or(4).

1.1.3.1 Compound Represented by Formula (2)

In formula (2), R³ is hydrogen or alkyl having 1 to 20 carbon atoms,wherein any —CH₂— in the alkyl can be substituted with —O—, —S—, —COO—,—OCO—, —CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl can besubstituted with halogen. Among them, preferably, R³ is alkyl having 1to 10 carbon atoms, wherein any —CH₂— in the alkyl can be substitutedwith —O—, —S—, —COO—, —OCO—, —CH═CH— or —C≡C—. More preferably, R³ isalkyl having 1 to 10 carbon atoms, wherein any —CH₂— in the alkyl can besubstituted with —O—, —CH═CH— or —C≡C—. Most preferably, R³ is alkylhaving 1 to 10 carbon atoms, wherein any —CH₂— in the alkyl can besubstituted with —O—.

In formula (2), R⁴ is halogen, —CN, —N═C═O, —N═C═S, —CF₃—, —OCF₃—,—C≡C—CN or —C≡C—CF₃. Among them, R⁴ is preferably halogen, —CN, —N═C═S,—CF₃, —C≡C—CN or —C≡C—CF₃.

In formula (2), A⁶, A⁷ and A⁸ are each independently an aromatic ornonaromatic 3- to 8-membered ring or a condensed ring having 9 or morecarbon atoms, wherein any hydrogen in these rings can be substitutedwith halogen, alkyl having 1 to 3 carbon atoms or alkyl halide; any—CH₂— in the rings can be substituted with —O—, —S— or —NH—; and —CH═can be substituted with —N═.

Among them, more preferably, A⁶, A⁷ and A⁸ are each independently abenzene ring, a naphthalene ring or a cyclohexane ring, wherein anyhydrogen in these rings can be substituted with halogen, alkyl having 1to 3 carbon atoms or alkyl halide; any —CH₂— in the rings can besubstituted with —O— or —S—; and —CH═ can be substituted with —N═. Evenmore preferably, A⁶, A⁷ and A⁸ are each independently a benzene ring, anaphthalene ring or a cyclohexane ring, wherein any hydrogen in theserings can be substituted with fluorine, chlorine, methyl or methylhalide; any —CH₂— in the rings can be substituted with —O— or —S—; and—CH═ can be substituted with —N═. Most preferably, A⁶, A⁷ and A⁸ areeach independently a benzene ring, a pyrimidine ring, a dioxane ring ora cyclohexane ring, wherein any hydrogen in the benzene ring can besubstituted with fluorine.

In formula (2), Z⁶ and Z⁷ are each independently a single bond oralkylene having 1 to 8 carbon atoms, wherein any —CH₂— in the alkylenecan be substituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —N═N—,—CH═N—, —N═CH—, —N(O)═N—, —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C—, and anyhydrogen in the alkylene can be substituted with halogen. Among them, Z⁶and Z⁷ are preferably a single bond or alkylene having 1 to 4 carbonatoms, wherein any —CH₂— in the alkylene can be substituted with —O—,—S—, —COO—, —OCO—, —CSO—, —OCS—, —CH═CH—, —CF═CF— or —C≡C—, and anyhydrogen in the alkylene can be substituted with halogen. Z⁶ and Z⁷ aremore preferably a single bond, —COO—, —CF₂O— or —C≡C—. Most preferably,Z⁶ is a single bond, —CF₂O— or —COO—.

In formula (2), n⁶ and n⁷ are each independently 0 or 1. Both n⁶ and n⁷are 1 only when at least one of Z⁶ and Z⁷ is —CF₂O—. Both n⁶ and n⁷ are0 when A⁷ or A⁸ is a condensed ring having 9 or more carbon atoms. Amongthem, preferably, Z⁷ is —CF₂O— and both n⁶ and n⁷ are 1; or Z⁷ is asingle bond or —COO—, n⁶ is 0 and n⁷ is 1.

1.1.3.2. Compound Represented by Formula (3)

In formula (3), R⁵ is alkyl having 1 to 10 carbon atoms, wherein any—CH₂— in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—,—CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl can besubstituted with halogen. Among them, R⁵ is preferably alkyl having 1 to10 carbon atoms, wherein any —CH₂— in the alkyl can be substituted with—O—, —CH═CH— or —C≡C—.

In formula (3), X^(a) is fluorine, chlorine, —CN, —N═C═S, —CF₃, —OCF₃,—C≡C—CN or —C≡C—CF₃.

In formula (3), Z¹² is a single bond, —COO— or —C≡C—, and among them,—COO— is preferable.

In formula (3), L⁸ to L¹¹ are each independently hydrogen or fluorine.Among them, preferably, L⁸ to L¹¹ are each independently hydrogen orfluorine, wherein at least two of them are fluorine.

1.1.3.3. Compound Represented by Formula (4)

In formula (4), R⁶ is alkyl having 1 to 10 carbon atoms, wherein any—CH₂— in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—,—CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl can besubstituted with halogen. Among them, R⁶ is preferably alkyl having 1 to10 carbon atoms, wherein any —CH₂— in the alkyl can be substituted with—O—, and —CH₂— nonadjacent to the aromatic ring can be substituted with—CH═CH—.

In formula (4), X^(b) is fluorine, chlorine, —CF₃, —OCF₃, —C═C—CF₃ or—C≡C—CF₃. Particularly preferably, X^(b) is fluorine, chlorine, —CF₃ or—OCF₃.

In formula (4), Z¹³ and Z¹⁴ are a single bond or —CF₂O—, wherein atleast one of them is —CF₂O—. More preferably, Z¹³ is a single bond.

In formula (4), L¹² to L¹⁷ are each independently hydrogen, chlorine orfluorine. Among them, preferably, L¹² to L¹⁷ are each independentlyhydrogen or fluorine, wherein at least two of them are fluorine.

1.1.4. Weight Ratio

When the clearing point of the component 1 is approximately 150 toapproximately 250° C., preferably, the component 1 is contained in anamount of approximately 10 to approximately 80 wt % and the component 2is contained in an amount of approximately 20 to approximately 90 wt %in the liquid crystal composition A. More preferably, the component 1 iscontained in an amount of approximately 30 to approximately 60 wt % andthe component 2 is contained in an amount of approximately 30 toapproximately 70 wt %. When the clearing point of the component 1 isapproximately 250 to approximately 400° C., preferably, the component 1is contained in an amount of approximately 5 to approximately 70 wt %and the component 2 is contained in an amount of approximately 30 toapproximately 95 wt % in the liquid crystal composition A. As describedabove, a plurality of compounds represented by formula (1) can becontained in the liquid crystal composition of the present invention asthe component 1, and similarly, a plurality of compounds represented byformula (2) can be contained as the component 2. Therefore, for example,when a plurality of compounds represented by formula (1) is contained,the total amount of the compounds represented by formula (1) isapproximately 10 to approximately 80 wt % (or approximately 5 toapproximately 70 wt %).

1.1.5. Temperature Range Allowing Coexistence of the Nematic Phase andthe Non-Liquid Crystalline Isotropic Phase or the Chiral Nematic Phaseand the Non-Liquid Crystalline Isotropic Phase

The liquid crystal composition A is a liquid crystal composition, whichexhibits the coexistence state of the nematic phase and the non-liquidcrystalline isotropic phase in the lowered temperature process when nochiral dopant is contained, and which exhibits the coexistence state ofthe chiral nematic phase and the non-liquid crystalline isotropic phasein the lowered temperature process when the chiral dopants arecontained. Further, the liquid crystal composition A is a compositionwhich does not exhibit an optically isotropic liquid crystal phase. Thecoexistence state of the nematic phase and the non-liquid crystallineisotropic phase or the coexistence state of the chiral nematic phase andthe non-liquid crystalline isotropic phase can be confirmed, forexample, by observation using a polarization microscope. Thesecoexistence states are not caused by temperature gradient with respectto the liquid crystal composition.

The liquid crystal composition A, which is a component in the liquidcrystal material of the present invention, preferably has a widetemperature range allowing coexistence of the nematic phase and thenon-liquid crystalline isotropic phase or the chiral nematic phase andthe non-liquid crystalline isotropic phase. Specifically, the differencebetween the upper limit and the lower limit of a temperature allowingthe coexistence of these phases is more preferably approximately 5 toapproximately 150° C. When the temperature range allowing thecoexistence of these phases is wide, the liquid crystal composition B(the liquid crystal material of the present invention), which isobtained by further adding the chiral dopants, tends to have anoptically isotropic liquid crystal phase in a wide temperature range. Inthe polymer/liquid crystal composite of the invention using the liquidcrystal composition B, birefringence does not easily remain afterelectric field elimination, and high speed response is realized.

When the chiral dopants are added to the liquid crystal composition A,in which the nematic phase and the non-liquid crystalline isotropicphase coexist in a wide temperature range, and which does not comprisethe chiral dopants, the liquid crystal composition A, in which thechiral nematic phase and the non-liquid crystalline isotropic phasecoexist in a wide temperature range, can be easily obtained.

The pitch of the chiral nematic phase, which does not coexist with thenon-liquid crystalline isotropic phase in the liquid crystal compositionA, is generally approximately 700 nm or more. As described later, whenthe chiral dopants are added, the liquid crystal composition B having ashorter pitch can be obtained.

1.2. Liquid Crystal Composition B

1.2.1. Composition of the Liquid Crystal Composition B

The liquid crystal composition B (liquid crystal material of theinvention) is a composition which exhibits an optically isotropic liquidcrystal phase. For example, the liquid crystal composition B can beobtained by further adding the chiral dopants to the liquid crystalcomposition A.

A liquid crystal composition, in which the chiral dopants are added inan amount of approximately 1 to approximately 40 wt %, preferably in anamount of approximately 5 to approximately 15 wt % of the total weightof the liquid crystal composition B, tends to have an opticallyisotropic liquid crystal phase, and therefore is preferable, though itdepends on the composition of the liquid crystal composition A, the typeof the chiral dopants to be added and the like.

In the step of producing the liquid crystal composition B, which ischaracterized by addition of the chiral dopants to the liquid crystalcomposition A, the chiral dopants which can be contained in the liquidcrystal composition A in advance and the chiral dopants which arefurther added in order to obtain the liquid crystal composition B may bethe same or different.

1.2.2 Clearing Point

In the liquid crystal composition B of the invention, the clearingpoints (T₁) and (T₂) of the components 1 and 2 contained in the liquidcrystal composition A and the clearing point (T×B) of the liquid crystalcomposition B as described later preferably satisfy the followingformulae:T₁>T₂T ₁ −T×B≧100° C.

More preferably, these clearing points satisfy the following formulae:T₁>T₂T ₁ −T×B≧150° C.

Particularly preferably, these clearing points satisfy the followingformulae:T₁>T₂T ₁ −T×B≧200° C.

1.2.3. Chiral Dopant

The chiral dopants contained in the liquid crystal composition B (liquidcrystal material of the invention) is preferably a compound having astrong helical twisting power. In the case of a compound having a stronghelical twisting power, an adding amount thereof required to obtain adesired pitch can be decreased, and therefore increase in drive voltagecan be suppressed, and it is practically advantageous. Specifically,compounds represented by the above-described formulae (K1) to (K5) arepreferable.

In formulae (K1) to (K5): each R^(K) is independently hydrogen, halogen,—CN, —N═C═O, —N═C═S or alkyl having 1 to 20 carbon atoms, wherein any—CH₂— in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—,—CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl can besubstituted with halogen; each A is independently an aromatic ornonaromatic 3- to 8-membered ring or a condensed ring having 9 or morecarbon atoms, wherein any hydrogen in these rings can be substitutedwith halogen, alkyl having 1 to 3 carbon atoms or haloalkyl; —CH₂— inthe rings can be substituted with —O—, —S— or —NH—, and —CH═ can besubstituted with —N═; each Z is independently a single bond or alkylenehaving 1 to 8 carbon atoms, wherein any —CH₂— can be substituted with—O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —N═N—, —CH═N—, —N═CH—, —N(O)═N—,—N═N(O)—, —CH═CH—, —CF═CF— or —C≡C—, and any hydrogen can be substitutedwith halogen; X is a single bond, —COO—, —OCO—, —CH₂O—, —OCH₂—, —CF₂O—,—OCF₂— or —CH₂CH₂—; and m is 1 to 4.

Among them, the chiral dopants contained in the liquid crystalcomposition B is preferably represented by formulae (K2-1) to (K2-8)included in formula (K2) and formulae (K5-1) to (K5-3) included informula (K5) (in the formulae, each R^(K) is independently alkyl having3 to 10 carbon atoms, wherein —CH₂— adjacent to the ring in the alkylcan be substituted with —O—, and any —CH₂— can be substituted with—CH═CH—).

The chiral dopants are contained preferably in an amount ofapproximately 1 to approximately 40 wt %, more preferably in an amountof approximately 3 to approximately 25 wt %, and most preferably in anamount of approximately 5 to approximately 15 wt % of the total weightof the liquid crystal composition B.

1.2.4. Optically Isotropic Liquid Crystal Phase

The liquid crystal composition B (liquid crystal material of theinvention) has an optically isotropic liquid crystal phase. “A liquidcrystal composition exhibits an optically isotropic liquid crystalphase” means that the composition shows optically isotropic nature sinceliquid crystal molecular alignment is macroscopically isotropic, butliquid crystalline order is microscopically present. The pitch based onthe liquid crystalline order, which the liquid crystal composition Bmicroscopically has, is preferably approximately 700 nm or less, morepreferably approximately 500 nm or less, and most preferablyapproximately 350 nm or less.

The term “non-liquid crystalline isotropic phase” means agenerally-defined isotropic phase, i.e., a disordered phase, wherein, ifthe phase is generated by a region whose local order parameter is notzero, the cause thereof is fluctuation. For example, an isotropic phasewhich is exhibited in the high temperature side of the nematic phasecorresponds to the non-liquid crystalline isotropic phase in the presentspecification. The same definition is applied to the chiral liquidcrystal in the present specification. Further, the term “opticallyisotropic liquid crystal phase” as used herein refers to a phase whichexhibits an optically isotropic (not fluctuant) liquid crystal phase.Examples thereof include a phase which exhibits a platelet texture (bluephase in a limited sense).

In general, the blue phase is classified into three types (blue phase I,blue phase II and blue phase III). All of the three types of blue phasesare optically active and optically isotropic. In the blue phases I andII, 2 or more types of diffracted lights attributed to Bragg reflectionsfrom different lattice planes are observed.

2. Polymer

The composite material of the invention can also be produced by mixingthe liquid crystal composition B (liquid crystal material of theinvention) with a polymer obtained in advance by means ofpolymerization. Preferably, the composite material is produced by mixingthe liquid crystal composition B with a low-molecular-weight monomer,macromonomer, oligomer or the like (hereinafter collectively referred toas “monomer and the like”), which is converted to a polymer, andthereafter by conducting polymerization reaction in the mixture. In thespecification, a mixture including the monomer and the like and theliquid crystal composition B is referred to as “polymerizablemonomer/liquid crystal mixture.” Depending on the necessity, the“polymerizable monomer/liquid crystal mixture” may contain apolymerization initiator, a curing agent, a catalyst, a stabilizationagent, a dichroism pigment, a photochromic compound or the like within arange in which the effects of the invention are not reduced, asdescribed later. For example, depending on the necessity, thepolymerizable monomer/liquid crystal mixture of the present inventionmay contain a polymerization initiator in an amount of approximately 0.1to approximately 20 parts by weight per 100 parts by weight of thepolymerizable monomer.

Polymerization temperature is preferably a temperature at which thepolymer/liquid crystal composite shows high transparency and isotropicnature. More preferably, polymerization is started at a temperature atwhich a mixture of the monomer and the liquid crystal material exhibitsthe isotropic phase or the blue phase and is terminated in the state ofthe isotropic phase or the optically isotropic liquid crystal phase.That is, polymerization temperature is preferably a polymerizationtemperature at which, after polymerization, the polymer/liquid crystalcomposite does not substantially scatter light which is nearer to thelong-wavelength side compared to the visible light and exhibits anoptically isotropic state.

For example, a low-molecular-weight monomer, macromonomer and oligomercan be used as a raw material monomer of a polymer constituting thecomposite material of the invention. In the present specification, thephrase “raw material monomer of a polymer” is intended to include alow-molecular-weight monomer, macromonomer, oligomer and the like.Further, a polymer to be obtained preferably has a three-dimensionalcross-linked structure. Therefore, as a raw material monomer of apolymer, a multifunctional monomer having 2 or more polymerizablefunctional groups is preferably used. The polymerizable functional groupis not particularly limited, and examples thereof include an acrylgroup, a methacryl group, a glycidyl group, an epoxy group, an oxetanylgroup, a vinyl group and the like. From the viewpoint of polymerizationvelocity, an acryl group and a methacryl group are preferred. In a rawmaterial monomer of a polymer, approximately 10 wt % or more of amonomer having 2 or more polymerizable functional groups is preferablycontained since the composite material of the invention tends to easilyshow high transparency and isotropic nature thereby.

Further, in order to obtain a suitable composite material, a polymerpreferably has a mesogenic moiety. A raw material monomer having amesogenic moiety can be used as a part or all of the raw materialmonomer of the polymer.

2.1. Monofunctional/Bifunctional Monomer Having a Mesogenic MoietyR^(a)—Y-(A^(M)-Z^(M)) p-A^(M)-Y—R^(b)  (M1)R^(b)—Y-(A^(M)-Z^(M)) p-A^(M)-Y—R^(b)  (M2)

In formula (M1), R^(a) is each independently hydrogen, halogen, —CN,—N═C═O, —N═C═S or alkyl having 1 to 20 carbon atoms, wherein any —CH₂—in the alkyl can be substituted with —O—, —S—, —CO—, —COO—, —OCO—,—CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl can besubstituted with halogen or —CN.

R^(a) is preferably hydrogen, halogen, —CN, —CF₃, —CF₂H, —CFH₂, —OCF₃,—OCF₂H, alkyl having 1 to 20 carbon atoms, alkoxy having 1 to 19 carbonatoms, alkenyl having 2 to 21 carbon atoms or alkynyl having 2 to 21carbon atoms. Particularly preferably, R^(a) is —CN, alkyl having 1 to20 carbon atoms or alkoxy having 1 to 19 carbon atoms. In formula (M1),R^(b) is each independently one of polymerizable groups represented by(M3-1) to (M3-7).

In formula (M2), R^(b) is each independently one of polymerizable groupsrepresented by (M3-1) to (M3-7).

Each R^(d) in the groups (M3-1) to (M3-7) is independently hydrogen,halogen or alkyl having 1 to 5 carbon atoms, wherein any hydrogen in thealkyl can be substituted with halogen. Preferably, R^(d) is hydrogen,halogen or methyl. Particularly preferably, R^(d) is hydrogen, fluorineor methyl.

Polymerization of the groups (M3-2), (M3-3), (M3-4) and (M3-7) issuitably conducted by means of radical polymerization. Polymerization ofthe groups (M3-1), (M3-5) and (M3-6) is suitably conducted by means ofcationic polymerization. Since both the polymerizations are livingpolymerization, they are initiated when a small amount of radical orcation active species is generated in a reaction system. Apolymerization initiator can be used in order to accelerate generationof active species. For example, light or heat can be used for generationof active species.

In formulae (M1) and (M2), A^(M) is each independently an aromatic ornonaromatic 5- or 6-membered ring or a condensed ring having 9 or morecarbon atoms, wherein —CH₂— in the rings can be substituted with —O—,—S—, —NH— or —NCH₃—; —CH═ in the rings can be substituted with —N═; anda hydrogen atom on the rings can be substituted with halogen, alkylhaving 1 to 5 carbon atoms or alkyl halide. Favorable examples of A^(M)include 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene,naphthalene-2,6-diyl, tetrahydronaphthalene-2,6-diyl, fluorene-2,7-diyland bicyclo[2.2.2]octane-1,4-diyl. In these rings, any —CH₂— can besubstituted with —O—, and any —CH═ can be substituted with —N═. Further,in these rings, any hydrogen can be substituted with halogen, alkylhaving 1 to 5 carbon atoms or alkyl halide having 1 to 5 carbon atoms.

In view of the stability of compounds, —CH₂—O—CH₂—O—, in which oxygenatoms are not adjacent to each other, is more preferable than—CH₂—O—O—CH₂—, in which oxygen atoms are adjacent to each other. Thesame applies to the case of sulfur atoms.

Among them, A^(M) is particularly preferably 1,4-cyclohexylene,1,4-cyclohexenylene, 1,4-phenylene, 2-fluoro-1,4-phenylene,2,3-difluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene,2,6-difluoro-1,4-phenylene, 2-methyl-1,4-phenylene,2-trifluoromethyl-1,4-phenylene, 2,3-bis(trifluoromethyl)-1,4-phenylene, naphthalene-2,6-diyl,tetrahydronaphthalene-2,6-diyl, fluorene-2,7-diyl,9-methylfluorene-2,7-diyl, 1,3-dioxane-2,5-diyl, pyridine-2,5-diyl orpyrimidine-2,5-diyl. The aforementioned 1,4-cyclohexylene and1,3-dioxane-2,5-diyl more preferably have trans-configuration comparedto cis-configuration.

2-fluoro-1,4-phenylene and 3-fluoro-1,4-phenylene are structurallyidentical, and therefore the latter is not listed herein. This rule isapplied to the relationship between 2,5-difluoro-1,4-phenylene and3,6-difluoro-1,4-phenylene and the like.

In formulae (M1) and (M2), Y is each independently a single bond oralkylene having 1 to 20 carbon atoms, wherein any —CH₂— in the alkylenecan be substituted with —O—, —S—, —CH═CH—, —C≡C—, —COO— or —OCO—.Preferably, Y is a single bond, —(CH₂)_(r)—, —O(CH₂)_(r)— or—(CH₂)_(r)O— (in the aforementioned formulae, r is an integer from 1 to20). Particularly preferably, Y is a single bond, —(CH₂)_(r)—,—O(CH₂)_(r)— or —(CH₂)_(r)O— (in the aforementioned formulae, r is aninteger from 1 to 10). In view of the stability of compounds,preferably, —Y—R^(a) and —Y—R^(b) do not have —O—O—, —O—S—, —S—O— or—S—S— in the groups thereof.

In formulae (M1) and (M2), Z^(M) is each independently a single bond,—(CH₂)_(q)—, —O(CH₂)_(q)—, —(CH₂)_(q)O—, —O(CH₂)_(q)O—, —CH═CH—, —C≡C—,—COO—, —OCO—, —(CF₂)₂—, —(CH₂)₂—COO—, —OCO—(CH₂)₂—, —CH═CH—COO—,—OCO—CH═CH—, —C≡C—COO—, —OCO—C≡C—, —CH═CH—(CH₂)₂—, —(CH₂)₂—CH═CH—,—CF═CF—, —C≡C—CH═CH—, —CH═CH—C≡C—, —OCF₂—(CH₂)₂—, —(CH₂)₂—CF₂O—, —OCF₂—or —CF₂O— (in the aforementioned formulae, q is an integer from 1 to20).

Preferably, Z^(M) is a single bond, —(CH₂)_(q)—, —O(CH₂)_(q)—,—(CH₂)_(q)O—, —CH═CH—, —C≡C—, —COO—, —OCO—, —(CH₂)₂—COO—, —OCO—(CH₂)₂—,—CH═CH—COO—, —OCO—CH═CH—, —OCF₂— or —CF₂O—.

In formulae (M1) and (M2), p is an integer from 1 to 6. Preferably, p isan integer from 1 to 3. When p is 1, the formulae represent a bicycliccompound having 2 rings such as 6-membered ring and the like. When p is2 or 3, the formulae represent a tricyclic compound or a tetracycliccompound, respectively. For example, when p is 1, two A^(M)s may be thesame or different. For example, when p is 2, three A^(M)s (or twoZ^(M)s) may be the same or different. The same applies to the case wherep is 3 to 6. The same applies to R^(a), R^(b), R^(d), Z^(M), A^(M) andY.

Compounds (M1) represented by formula (M1) and compounds (M2)represented by formula (M2) can be suitably used since they have thesame properties even if they include an isotope such as ²H (deuterium)and ¹³C in an amount which is more than the amount represented by thenaturally-occurring ratio.

More favorable examples of the compounds (M1) and (M2) include compounds(M1-1) to (M1-41) and (M2-1) to (M2-27) represented by the followingformulae (M1-1) to (M1-41) and (M2-1) to (M2-27). In these compounds,meanings of R^(a), R^(b), R^(d), Z^(M), A^(M), Y and p are the same asthose in the formulae (M1) and (M2) described in the embodiment of theinvention.

Hereinafter, partial structures as shown below in the compounds (M1-1)to (M1-41) and (M2-1) to (M2-27) will be explained. The partialstructure (a1) represents 1,4-phenylene in which any hydrogen issubstituted with fluorine. The partial structure (a2) represents1,4-phenylene in which any hydrogen can be substituted with fluorine.The partial structure (a3) represents 1,4-phenylene in which anyhydrogen can be substituted with fluorine or methyl. The partialstructure (a4) represents fluorene in which hydrogen at position 9 canbe substituted with methyl.

Monomers not having the aforementioned mesogenic moiety andpolymerizable compounds other than the monomers (M1) and (M2) having themesogenic moiety can be used according to need.

In order to optimize the optically isotropic liquid crystal phase of thepolymer/liquid crystal composite of the invention, a monomer having themesogenic moiety and 3 or more polymerizable functional groups can beused. As the monomer having the mesogenic moiety and 3 or morepolymerizable functional groups, a publicly-known compound can besuitably used. Examples thereof include compounds represented by (M4-1)to (M4-3). More specifically, examples thereof include compoundsdescribed in Japanese Laid-Open Patent Publication Nos. 2000-327632,2004-182949 and 2004-59772. In (M4-1) to (M4-3), meanings of R^(b), Za,Y and (F) are the same as those described above.

Monomer Which Does Not Have the Mesogenic Moiety but has a PolymerizableFunctional Group

Examples of monomers which do not have the mesogenic moiety but have apolymerizable functional group include, but are not limited to, linearor branched acrylate having 1 to 30 carbon atoms and linear or brancheddiacrylate having 1 to 30 carbon atoms. Examples of monomers which donot have the mesogenic moiety but have 3 or more polymerizablefunctional groups include, but are not limited to, glycerol propoxylate(1 PO/OH) triacrylate, pentaerythritol propoxylate triacrylate,pentaerythritol triacrylate, trimethylolpropane ethoxylate triacrylate,trimethylolpropane propoxylate triacrylate, trimethylolpropanetriacrylate, di(trimethylolpropane) tetraacrylate, pentaerythritoltetraacrylate, di(pentaerythritol) pentaacrylate, di(pentaerythritol)hexaacrylate, and trimethylolpropane triacrylate.

2.3. Polymerization Initiator

Polymerization reaction in the production of the polymer constitutingthe composite material of the present invention is not particularlylimited. For example, photo radical polymerization, thermal radicalpolymerization, photo cation polymerization and the like can beconducted.

Examples of photo radical polymerization initiators, which can be usedin photo radical polymerization, include DAROCUR® 1173 and 4265 (tradenames; Ciba Specialty Chemicals Inc.) and IRGACURE® 184, 369, 500, 651,784, 819, 907, 1300, 1700, 1800, 1850 and 2959 (trade names; CibaSpecialty Chemicals Inc.).

Examples of favorable initiators which can be used in thermal radicalpolymerization include benzoyl peroxide, diisopropyl peroxydicarbonate,t-butylperoxy-2-ethylhexanoate, t-butyl peroxypivalate, t-butylperoxydiisobutyrate, lauroyl peroxide, dimethyl 2,2′-azobis(isobutyrate)(MAIB), di-t-butylperoxide (DTBPO), azobisisobutyronitrile (AIBN), andazobiscyclohexanecarbonitrile (ACN).

Examples of photo cation polymerization initiators, which can be used inphoto cation polymerization, include diaryliodonium salt (hereinafterreferred to as “DAS”), triarylsulfonium salt (hereinafter referred to as“TAS”) and the like.

Examples of DAS include diphenyliodonium tetrafluoroborate,diphenyliodonium hexafluorophosphonate, diphenyliodoniumhexafluoroarsenate, diphenyliodonium trifluoromethanesulfonate,diphenyliodonium trifluoroacetate, diphenyliodonium-p-toluene sulfonate,diphenyliodonium tetra(pentafluorophenyl)borate,4-methoxyphenylphenyliodonium tetrafluoroborate,4-methoxyphenylphenyliodonium hexafluorophosphonate,4-methoxyphenylphenyliodonium hexafluoroarsenate,4-methoxyphenylphenyliodonium trifluoromethanesulfonate,4-methoxyphenylphenyliodonium trifluoroacetate,4-methoxyphenylphenyliodonium-p-toluene sulfonate and the like.

DAS can be supersensitized by adding thereto a photosensitizer such asthioxanthone, phenothiazine, chlorothioxanthone, xanthone, anthracene,diphenylanthracene, rubrene and the like.

Examples of TAS include triphenylsulfonium tetrafluoroborate,triphenylsulfonium hexafluorophosphonate, triphenylsulfoniumhexafluoroarsenate, triphenylsulfonium trifluoromethanesulfonate,triphenylsulfonium trifluoroacetate, triphenylsulfonium-p-toluenesulfonate, triphenylsulfonium tetra(pentafluorophenyl)borate,4-methoxyphenyldiphenylsulfonium tetrafluoroborate,4-methoxyphenyldiphenylsulfonium hexafluorophosphonate,4-methoxyphenyldiphenylsulfonium hexafluoroarsenate,4-methoxyphenyldiphenylsulfonium trifluoromethanesulfonate,4-methoxyphenyldiphenylsulfonium trifluoroacetate,4-methoxyphenyldiphenylsulfonium-p-toluene sulfonate and the like.

Examples of specific trade names of photo cation polymerizationinitiators include: Cyracure® UVI-6990, Cyracure® UVI-6974 and Cyracure®UVI-6992 (trade names, UCC); ADEKA OPTOMER SP-150, SP-152, SP-170 andSP-172 (trade names, ADEKA Corporation); Rhodorsil Photoinitiator 2074(trade name, Rhodia Japan, Ltd.); IRGACURE® 250 (trade name, CibaSpecialty Chemicals Inc.); UV-9380C (trade name, GE Toshiba SiliconesCo., Ltd.) and the like.

2.4. Curing Agent and the Like

In the production of the polymer constituting the composite material ofthe invention, in addition to the aforementioned monomers and the likeand the polymerization initiator, one or more types of other suitablecomponents, e.g., a curing agent, a catalyst, a stabilizer and the likecan also be added.

As the curing agent, a conventionally known latent curing agent, whichis used as a curing agent for epoxy resin, can be generally used.Examples of latent curing agents for epoxy resin include amine-basedcuring agents, novolac resin-based curing agents, imidazole-based curingagents, acid anhydride-based curing agents and the like. Examples ofamine-based curing agents include: aliphatic polyamines such asdiethylenetriamine, triethylenetetraamine, tetraethylenepentaamine,m-xylenediamine, trimethylhexamethylenediamine,2-methylpentamethylenediamine and diethylaminopropylamine; alicyclicpolyamines such as isophoronediamine, 1,3-bisaminomethylcyclohexane,bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexaneand Laromin; and aromatic polyamines such as diaminodiphenylmethane,diaminodiphenylethane and meta-phenylenediamine.

Examples of novolac resin-based curing agents include phenol novolacresin and bisphenol novolac resin. Examples of imidazole-based curingagents include 2-methylimidazole, 2-ethylhexylimidazole,2-phenylimidazole and 1-cyanoethyl-2-phenylimidazolium trimellitate.

Examples of acid anhydride-based curing agents includetetrahydrophthalic anhydride, hexahydrophthalic anhydride,methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride,methylcyclohexene tetracarboxylic dianhydride, phthalic anhydride,trimellitic anhydride, pyromellitic anhydride and benzophenonetetracarboxylic dianhydride.

Moreover, a curing accelerator can be additionally used in order toaccelerate curing reaction between a polymerizable compound having aglycidyl group, an epoxy group or an oxetanyl group and a curing agent.Examples of curing accelerators include: tertiary amines such asbenzyldimethylamine, tris(dimethylaminomethyl)phenol anddimethylcyclohexylamine; imidazoles such as1-cyanoethyl-2-ethyl-4-methylimidazole and 2-ethyl-4-methylimidazole;organic phosphorus-based compounds such as triphenylphosphine;quaternary phosphonium salts such as tetraphenylphosphoniumbromide;diazabicycloalkenes such as 1,8-diazabicyclo[5.4.0]undecene-7, organicacid salt thereof and the like; quaternary ammonium salts such astetraethylammoniumbromide and tetrabutylammoniumbromide; and boroncompounds such as boron trifluoride and triphenylborate. These curingaccelerators can be used solely or in combination.

For example, in order to prevent undesired polymerization duringpreservation, a stabilizer is preferably added. As the stabilizer, anycompound known as a stabilizer in the art can be used. Typical examplesof stabilizers include 4-ethoxyphenol, hydroquinone and butylatedhydroxytoluene (BHT).

3. Content Percentage of Liquid Crystal Material and the Like

The content percentage of the liquid crystal material in thepolymer/liquid crystal composite of the invention (e.g., the liquidcrystal composition B) is preferably as high as possible within a rangein which the composite can exhibit the optically isotropic liquidcrystal phase. The higher the content percentage of the liquid crystalmaterial, the higher the Kerr constant of the composite of theinvention.

In the polymer/liquid crystal composite of the invention, the contentpercentage of the liquid crystal material is preferably approximately 60to approximately 99 wt %, more preferably approximately 60 toapproximately 95 wt %, and particularly preferably approximately 65 toapproximately 95 wt % of the total amount of the composite. The contentpercentage of the polymer is preferably approximately 1 to approximately40 wt %, more preferably approximately 5 to approximately 40 wt %, andparticularly preferably approximately 5 to approximately 35 wt % of thetotal amount of the composite.

4. Others

The polymer/liquid crystal composite of the invention may contain, forexample, a dichroism pigment, a photochromic compound or the like withina range in which the effects of the present invention are not reduced.

Positive/negative of the dielectric anisotropy of the liquid crystalcomposition a of the invention is not particularly limited, but positiveis preferable. With respect to the absolute value of the value ofdielectric anisotropy of the liquid crystal composition a (Δ∈) and thevalue of optical anistropy anisotropy (Δn), the higher these values, thehigher the electric birefringence, and therefore these values arepreferably as high as possible.

EXAMPLES

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the invention and specificexamples provided herein without departing from the spirit or scope ofthe invention. Thus, it is intended that the invention covers themodifications and variations of this invention that come within thescope of any claims and their equivalents.

The following examples are for illustrative purposes only and are notintended, nor should they be interpreted to, limit the scope of theinvention.

In the examples of the specification, “I” represents the non-liquidcrystalline isotropic phase; “N” represents the nematic phase; “N*”represents the chiral nematic phase; and “BP” and “BPX” represent theblue phase or the optically isotropic liquid crystal phase. Coexistencestate of two phases is sometimes described in the following form:(N*+I), (N*+BP), etc. Specifically, (N*+I) represents a phase in whichthe non-liquid crystalline isotropic phase and the chiral nematic phasecoexist, and (N*+BP) represents a phase in which the BP phase or theoptically isotropic liquid crystal phase and the chiral nematic phasecoexist. “Un” represents an unconfirmed phase which is not opticallyisotropic.

In the specification, I-N phase transition point is sometimes referredto as N-I point, and I-N* transition point is sometimes referred to asN*-I point. Further, I-BP phase transition point is sometimes referredto as BP-I point.

In the examples of the specification, measurement/calculation of valuesof physical properties and the like is made according to the methoddescribed in the Standard of Electronic Industries Association of Japan,EIAJ•ED-2521A, unless otherwise indicated. Specific methods ofmeasurement, calculation and the like are as described below.

Phase Transition Point

A sample was placed on a hotplate of a melting-point measuring apparatusequipped with a polarization microscope. Initially, under crossednicols, temperature was elevated to the point at which the samplebecomes the non-liquid crystalline isotropic phase, and thereaftertemperature was lowered at the rate of 1° C./minute, and the chiralnematic phase or the optically anisotropic phase was allowed to becompletely exhibited. Phase transition temperature in the process wasmeasured. Next, temperature was elevated at the rate of 1° C./minute,and phase transition temperature in this process was measured. When itwas difficult to determine the phase transition point in the opticallyisotropic liquid crystal phase in dark field under crossed nicols, apolarization plate was inclined at an angle of 1 to 10° from the stateof the crossed nicols to measure the phase transition temperature.

Method for Calculating a Liquid Crystal Phase-Non-Liquid CrystallineIsotropic Phase Transition Point Using an Extrapolation Method

A nematic liquid crystal composition including 85 wt % of mother liquidcrystal having the nematic phase and 15 wt % of liquid crystallinecompound or liquid crystalline composition was prepared. Linearextrapolation was made using the liquid crystal phase-non-liquidcrystalline isotropic phase transition points of the mother liquidcrystal and the liquid crystalline compound or liquid crystallinecomposition to determine the liquid crystal phase-non-liquid crystallineisotropic phase transition point of the liquid crystalline compound orthe liquid crystalline composition.

Lower Limit of Temperature of Nematic Phase (TC; ° C.)

A sample having the nematic phase was put into a glass bottle, and itwas held in a freezer at 0° C., −10° C., −20° C., −30° C. and −40° C.for 10 days, and thereafter the liquid crystal phase was observed. Forexample, regarding the case where the nematic phase remained in thesample at −20° C. and it changed to crystal or smectic phase at −30° C.,it was described as TC≦−20° C. The lower limit of temperature of thenematic phase is sometimes abbreviated as “lower limit of temperature.”

Viscosity (η; Measured at 20° C.; mPa·s)

An E-type viscometer was used to measure viscosity.

Optical Anisotropy (Refractive Index Anisotropy; Δn; Measured at 25°C.):

Measurement was conducted with an Abbe refractometer, in which apolarization plate is provided to an eyepiece, using light having awavelength of 589 nm. After the surface of a main prism was rubbed inone direction, the sample was dropped on the main prism. The refractiveindex n∥ was measured when the direction of polarized light was parallelto the direction of rubbing. The refractive index n⊥ was measured whenthe direction of polarized light was perpendicular to the direction ofrubbing. Calculation was made using the following formula: Δn=n∥−n⊥.

Dielectric Anisotropy (Δ∈; Measured at 25° C.)

1. Liquid Crystal Composition a Whose Dielectric Anisotropy is Positive

The sample was put into a TN cell in which the gap between two glasssubstrates was about 9 μm and the twist angle was 80°. A sine wave (10V,1 kHz) was applied on the cell, and 2 seconds later, the permittivity ofliquid crystal molecules in the major axis direction (∈∥) was measured.A sine wave (0.5V, 1 kHz) was applied on the cell, and 2 seconds later,the permittivity of liquid crystal molecules in the minor axis direction(∈⊥) was measured. The value of dielectric anisotropy was calculatedusing the following formula: Δ∈=∈∥−∈⊥.

2. Liquid Crystal Composition a Whose Dielectric Anisotropy is Negative

The sample was put into a liquid crystal cell treated to have ahomeotropic alignment in which the gap between two glass substrates wasabout 9 μm. A sine wave (0.5V, 1 kHz) was applied on the cell, and 2seconds later, the permittivity (∈∥) was measured. Further, the samplewas put into a liquid crystal cell treated to have a homogeneousalignment in which the gap between two glass substrates was about 9 μm.A sine wave (0.5V, 1 kHz) was applied on the cell, and 2 seconds later,the permittivity (∈⊥) was measured. The value of dielectric anisotropywas calculated using the following formula: Δ∈=∈∥−∈⊥.

Voltage Holding Ratio (VHR; Measured at 25° C.; %)

The TN element used in the measurement had a polyimide-aligned film, andthe cell gap was 6 μm. After putting the sample into the element, it wassealed with an adhesive which is polymerized by ultraviolet. A pulsevoltage (5V for 60 μs) was applied on the TN element for charging.Attenuating voltage was measured for 16.7 msec using a high-speedvoltmeter, and an area between the voltage curve and the horizontal axisin a cycle was calculated. Further, from the wave pattern of voltagemeasured after removing the TN element, an area was similarlycalculated. Voltage holding ratio was calculated by comparison betweenthe two areas.

Pitch (P; Measured at 25° C.; nm)

Pitch length was measured using selective reflection (Handbook of LiquidCrystal, page 196 (published in 2000, Maruzen)). The selectivereflection wavelength λ satisfies the following relational expression:<n>p/λ=1. <n> represents the average refractive index, which iscalculated using the following formula: <n>={(n∥²+n⊥²)/2}^(1/2). Theselective reflection wavelength was measured using amicrospectrophotometer (JEOL Ltd., trade name: MSV-350). The pitch wascalculated by dividing the obtained reflection wavelength by the averagerefractive index.

The pitch of cholesteric liquid crystal having a reflection wavelengthin a longer-wavelength region compared to visible light is proportionalto the inverse number of the concentration of chiral dopants in a regionwhere the concentration of the chiral dopant is low. Therefore, thepitch was determined by measuring pitch length of liquid crystal havinga selective reflection wavelength in the visible light region at severalpoints and applying the linear extrapolation method thereto.

Example 1

Preparation of Liquid Crystal Composition

A nematic liquid crystal composition A-1 was prepared by mixingcompounds represented by the following formulae (a) to (f) and (g) inthe weight ratio shown below. Specifically, the composition was preparedby mixing: compounds (a) and (b) having the clearing point (N-I point)of 250° C. or more, as compounds corresponding to the component 1represented by the above-described formula (1); compound (g) having theK-I point of 49.8° C. and the clearing point of 7.7° C., as a compoundcorresponding to the component 2 represented by the above-describedformula (3); and compounds (c) to (f). Values shown at the right side ofvalues of the weight ratio are phase transition temperatures ofrespective compounds. The clearing point of the compound (g) was 7.7° C.The clearing point of the composition was given as an extrapolationvalue of N-I point, which was measured after mixing 15 wt % of compound(g) with the mother liquid crystal ZLI-1132 (manufactured by Merck).

(a) 5.2% K 69.0 Sx 231.2 N >250 I

(b) 5.2% K 64.4 Sx >250 N >250 I

(c) 9.9% K 40.6 N (33.1) I

(d) 9.9% K 35.7 N (33.1) I

(e) 9.9% K 29.5 N 58.2 I

(f) 9.9% K 39.9 N 64.71

(g) 50.0%

Next, a chiral dopant ISO-6OBA2 represented by the following formula wasadded to the liquid crystal composition A-1 to obtain liquid crystalcompositions A-2, A-3, A-4 and A-5. Specifically, as shown in Table 1,liquid crystal compositions, in which the concentrations of chiraldopants are 2.9, 5.0, 8.1 and 10.0 wt %, respectively, were prepared anddesignated as liquid crystal compositions A-2, A-3, A-4 and A-5,respectively. Further, each of the liquid crystal compositions A-1 toA-5 was held in a cell consisting of two ITO-glasses which was notsubjected to aligning treatment (cell thickness: 13 μm), and phasetransition temperatures were measured using a polarization microscope.

TABLE 1

ISO-6OBA2 N* + 1 BP Liquid crystal concentration temperature temperaturecomposition (wt %) Conditions Phase transition temperature (° C.) range(° C.) range (° C.) A-1 0.0 Lowering I-60.0-(N + 1)-54.0-N (6.0)temperature(1° C./min) Elevating N-56.5-(N + 1)-62-I temperature(1°C./min) A-2 2.9 Lowering I-54.7-(N* + 1)-48.6-N* 6.1 temperature(1°C./min) Elevating N*-51.5-(N* + 1)-57.3-I temperature(1° C./min) A-3 5.0Lowering I-50.9-(N* + 1)-42.9-N*   8 temperature(1° C./min) ElevatingN*-45.3-(BP + N*)-46.1-BP-51.0-(N* + 1)-52.9-I 4.9 temperature(1°C./min) A-4 8.1 Lowering I-42.9-(BP + 1)-38.0-BP-32.5-N* temperature(1°C./min) Elevating N*-34.7-BP-41.9-(BP + 1)-44.9-I 7.2~10.2temperature(1° C./min) A-5 10.0 Lowering temperature(1° C./min)Elevating N*-30.0-BP-40-I 10 temperature(1° C./min)

Phase transition temperatures of the liquid crystal compositions A-1 toA-5 are as shown in Table 1. Specifically, in the case of the liquidcrystal composition A-1, the difference between the upper limit (60° C.)and the lower limit (54° C.) of a temperature allowing coexistence ofthe nematic phase (N) and the non-liquid crystalline isotropic phase (I)(coexistence temperature range) in the lowered temperature process of−1° C./min was 6.0° C. In the case of the liquid crystal compositionA-2, the difference between the upper limit (54.7° C.) and the lowerlimit (48.6° C.) of a temperature allowing coexistence of the chiralnematic phase (N*) and the non-liquid crystalline isotropic phase (I)(coexistence temperature range) in the lowered temperature process of−1° C./min was 6.1° C.

In the case of the liquid crystal composition A-3, in the elevatedtemperature process of 1° C./min, the difference between the upper limit(51.0° C.) and the lower limit (46.1° C.) of a temperature at which theoptically isotropic liquid crystal phase was exhibited (BP temperaturerange) was 4.9° C.

In the case of the liquid crystal composition A-4, in the elevatedtemperature process of 1° C./min, the difference between the upper limit(41.9 to 44.9° C.) and the lower limit (34.7° C.) of a temperature atwhich the optically isotropic liquid crystal phase was exhibited (BPtemperature range) was 7.2 to 10.2° C. Similarly, the BP temperaturerange of the liquid crystal composition A-5 was 10° C. Thus, the liquidcrystal compositions A-4 and A-5 exhibited the optically isotropicliquid crystal phase in wide temperature ranges in the elevatedtemperature process. Therefore, among the liquid crystal compositionsA-1 to A-5 in this example, A-3, A-4 and A-5 correspond to the liquidcrystal composition B defined herein.

Moreover, according to the polarization microscope images of the liquidcrystal composition A-2 in the lowered temperature process at 54.5° C.,52° C. and 49° C. (FIG. 1), it was found that the non-liquid crystallineisotropic phase coexists with the chiral nematic phase in the liquidcrystal composition.

A mixture in which the compounds (a) and (b) corresponding to thecomponent 1 were mixed in the same weight ratio as that in the liquidcrystal compositions A-1 to A-5 (compound (a):compound (b)=5.2:5.2) wasprepared. When the N-I point (clearing point) of the mixture (T₁) wasmeasured, it was 270° C. or more. Since the N-I point (clearing point)of the liquid crystal composition A-1 (Tx) was 56.5° C., (T₁−Tx) was213.5° C. or more. Further, since the N*-I point (clearing point) of theliquid crystal composition A-2 (Tx) was 51.5° C., (T₁−Tx) was 218.5° C.or more.

Similarly, values of T₁−T×B in the cases of the liquid crystalcompositions A-3 to A-5 were as described below. T×B represents theclearing point of the liquid crystal composition B.Liquid crystal composition A-3: T ₁ −T×B=270° C. or more−51.0° C.=219.0°C. or moreLiquid crystal composition A-4: T ₁ −T×B=270° C. or more−41.9° C.=228.1°C. or moreLiquid crystal composition A-5: T ₁ −T×B=270° C. or more−40° C.=230° C.or more

Further, since the clearing point of the compound (g) corresponding tothe component 2 is 7.7° C., T₂ of the liquid crystal compositions A-3,A-4 and A-5 is 7.7° C.

Since T₁ of the liquid crystal compositions A-3, A-4 and A-5 is 270° C.,these liquid crystal compositions satisfy T₁>T₂.

Preparation of Mixture of Monomer and Liquid Crystal Material

As a mixture of the liquid crystal material and the monomer, 79.4 wt %of liquid crystal composition A-5, 8.6 wt % of trimethylolpropanetriacrylate, 11.4 wt % of1,4-di(4-(6-(acryloyloxy)hexyloxy)benzoyloxy)-2-methylbenzene and 0.6 wt% of 2,2′-dimethoxyphenylacetophenone (as a photopolymerizationinitiator) were mixed to prepare a liquid crystal composition A-5M.

Preparation of Polymer/Liquid Crystal Composite

The liquid crystal composition A-5M was held between a comb-likeelectrode substrate which is not subjected to alignment treatment and anopposed glass substrate (no electrode was provided thereto) (cellthickness: 12 μm), and the obtained cell was heated to have an isotropicphase at 35.0° C. In this state, ultraviolet (ultraviolet strength: 10mWcm⁻² (365 nm)) was irradiated for 5 minutes to conduct polymerizationreaction.

In the polymer/liquid crystal composite A-5P thus obtained, theoptically isotropic liquid crystal phase, in which diffracted light withtwo or more colors was not shown even if cooled to temperature of 0° C.or lower, was maintained. That is, the temperature range in which theoptically isotropic phase is exhibited was further broadened compared tothe case of the liquid crystal composition A-5.

As shown in FIG. 2, as electrodes of the comb-like electrode substrate,an electrode 1 extending from the left side and an electrode 2 extendingfrom the right side alternate with each other. Therefore, when there isa potential difference between the electrode 1 and the electrode 2, thecomb-like electrode substrate as shown in FIG. 2 can provide a state inwhich two electric fields with different direction (upward and downward)are present.

Example 2

A cell in which the polymer/liquid crystal composite A-5P obtained inExample 1 was held was set the optical system shown in FIG. 3 to measureelectrooptic characteristics. The aforementioned cell was set in theoptical system so that the incidence angle of laser light wasperpendicular to the cell surface and the line direction of thecomb-like electrode was 45° with respect to polarization plates ofPolarizer and Analyzer, respectively. When a rectangular wave having theamplitude of 180 V was applied, the transmission rate was 88% at ameasurement temperature of 20° C., and the transmitted light intensitywas saturated. When detected using a photodetector, the transmittedlight intensity at the time when no electric field was applied was 0.08,and the transmitted light intensity at the time when electric field wasapplied was 252. When the contrast was calculated, it was 3150. Theresponse speed during rise time (time required for change of transmittedlight intensity from 10% to 90% of the intensity at the time of applyingelectric field) was 170 μs, and the speed during fall time (timerequired for change of the transmitted light intensity from 90% to 10%of the intensity at the time of applying electric field) was 120 μs.

Further, even after removing electric field, residual birefringence wasnot observed. When turning on/off electric field was similarly triedwith the temperature changed in a range of 0 to 35° C., it was confirmedthat two states (a bright state and a dark state) appear within thistemperature range.

Thus, in the case of the polymer/liquid crystal composite A-5P, twostates (a bright state and a dark state) were successfully realized byturning on/off electric field, and high speed response was successfullyrealized even when electric field was applied until the transmissionrate was saturated.

Example 3

Preparation of Liquid Crystal Composition

A nematic liquid crystal composition F-1 was prepared by mixingcompounds represented by the following formulae (o-1), (o-2), (o-3) and(p) in the weight ratio described below. Specifically, the compositionwas prepared by mixing: compounds (o-1) to (o-3) having the N-I point(clearing point) of 250° C. or higher, as compounds corresponding to thecomponent 1 represented by the above-described formula (1); and compound(p) having the K-I point of 21.4° C. and the clearing point(extrapolation value) of −41.6° C., as a compound corresponding to thecomponent 2 represented by the above-described formula (3). Values shownat the right side of values of the weight ratio are phase transitiontemperatures of respective compounds.

(o-1) 16.6% K 102.9 N 258.7 I

(o-2) 16.7% K 98.4 N 255.2 I

(o-3) 16.7% K 87.8 N 251.5 I

(p) 50.0% K 21.4 I

Next, a chiral dopant ISO-6OBA2 was added to the liquid crystalcomposition F-1 to obtain liquid crystal compositions F-2 and F-3.Specifically, as shown in Table 2, liquid crystal compositions, in whichthe concentrations of chiral dopants are 0.8 and 10.0 wt %,respectively, were prepared and designated as liquid crystalcompositions F-2 and F-3, respectively. Further, each of the liquidcrystal compositions F-2 and F-3 was held in a cell consisting of twoITO-glasses which was not subjected to aligning treatment (cellthickness: 13 μm), and phase transition temperatures were measured usinga polarization microscope. In this regard, the clearing point of F-3 wasdetermined as follows: the same cell as that used in Example 1 was used;an alternating sine wave (80 V) was applied on F-3 and observation wasconducted using a polarization microscope; and a temperature at whichthe transmission rate was rapidly decreased under the elevatedtemperature condition was determined as the clearing point.

TABLE 2 ISO-6OBA2 N* + I BP Liquid crystal concentration temperaturetemperature composition (wt %) Conditions Phase transition temperature(° C.) range (° C.) range (° C.) F-1 0.0 Lowering I − 98.7 − (N + I) −85 − N (13.7) temperature (1° C./min) Elevating N − 89.2 − (N + I) − 101− I temperature (1° C./min) F-2 0.8 Lowering I − 97.2 − (N* + I) − 81 −N* 16.2 temperature (1° C./min) Elevating N* − 84 − (N* + I) − 101 − Itemperature (1° C./min) F-3 10.0 Lowering temperature (1° C./min)Elevating N* − 54 − (BPX or BP) − 74 − I 20 temperature (1° C./min)

Phase transition temperatures of the liquid crystal compositions F-1 toF-3 were as shown in Table 2. Specifically, in the case of the liquidcrystal composition F-1, the difference between the upper limit (98.7°C.) and the lower limit (85° C.) of a temperature allowing coexistenceof the nematic phase (N) and the non-liquid crystalline isotropic phase(I) (coexistence temperature range) in the lowered temperature processof −1° C./min was 13.7° C. In the case of the liquid crystal compositionF-2, the difference between the upper limit (97.2° C.) and the lowerlimit (81° C.) of a temperature allowing coexistence of the chiralnematic phase (N*) and the non-liquid crystalline isotropic phase (I)(coexistence temperature range) in the lowered temperature process of−1° C./min was 16.2° C.

In the case of the liquid crystal composition F-3, in the elevatedtemperature process of 1° C./min, the difference between the upper limit(74° C.) and the lower limit (54° C.) of a temperature at which theoptically isotropic liquid crystal phase was exhibited (BP(X) or BPtemperature range) was 20° C. Thus, the liquid crystal composition F-3exhibited the optically isotropic liquid crystal phase in the widetemperature range in the elevated temperature process.

A mixture in which the compounds (o-1), (o-2) and (o-3) corresponding tothe component 1 were mixed in the same weight ratio as that in theliquid crystal compositions F-1 to F-3 (compound (o-1):compound(o-2):compound (o-3)=16.6:16.7:16.7) was prepared. When the N-I point(clearing point) of the mixture (T₁) was measured, it was 254° C. Sincethe N-I point (clearing point) of the liquid crystal composition F-1(Tx) was 89.2° C., (T₁−Tx) was 164.8° C. or more. Since the N*-I point(clearing point) of the liquid crystal composition F-2 (Tx) was 84° C.,(T₁−Tx) was 170° C. Since the BP (or BPX)-I point (clearing point) ofthe liquid crystal composition F-3 (T×B) was 74° C., (T₁−T×B) was 180°C.

Further, since the clearing point of the compound (p) corresponding tothe component 2 was −41.6° C., T₂ of the liquid crystal composition F-3is −41.6° C.

Since T₁ of the liquid crystal composition F-3 is 254° C., these liquidcrystal compositions satisfy T₁>T₂.

Preparation of Mixture of Monomer and Liquid Crystal Material

As a mixture of the liquid crystal material and the monomer, 79.4 wt %of liquid crystal composition F-3, 8.6 wt % of dodecylacrylate, 11.4 wt% of 1,4-di(4-(6-(acryloyloxy)hexyloxy)benzoyloxy)-2-methylbenzene and0.6 wt % of 2,2′-dimethoxyphenylacetophenone (as a photopolymerizationinitiator) were mixed to prepare a liquid crystal composition F-3M.

Preparation of Polymer/Liquid Crystal Composite

The liquid crystal composition F-3M was held between a comb-likeelectrode substrate which was not subjected to alignment treatment andan opposed glass substrate (no electrode was provided thereto) (cellthickness: 12 μm), and the obtained cell was heated to have an isotropicphase at 65.0° C. In this state, ultraviolet (ultraviolet strength: 10mWcm⁻² (365 nm)) was irradiated for 5 minutes to conduct polymerizationreaction.

In the polymer/liquid crystal composite F-3P thus obtained, theoptically isotropic liquid crystal phase, in which diffracted light withtwo or more colors was not shown even if cooled to 30° C., wasmaintained. That is, the temperature range in which the opticallyisotropic phase is exhibited was further broadened compared to the caseof the liquid crystal composition F-3.

As shown in FIG. 2, as electrodes of the comb-like electrode substrate,an electrode 1 extending from the left side and an electrode 2 extendingfrom the right side alternate with each other. Therefore, when there isa potential difference between the electrode 1 and the electrode 2, thecomb-like electrode substrate as shown in FIG. 2 can provide a state inwhich two electric fields with different direction (upward and downward)are present.

A cell in which the polymer/liquid crystal composite F-3P obtained inExample 3 was held was set in the optical system shown in FIG. 3 tomeasure electrooptic characteristics. The aforementioned cell was set inthe optical system so that the incidence angle of laser light wasperpendicular to the cell surface and the line direction of thecomb-like electrode was 45° with respect to polarization plates ofPolarizer and Analyzer, respectively. A rectangular wave having theamplitude of 180 V was applied with a measurement temperature of 55° C.It did not lead to saturation of the transmission rate, but a brightstate was successfully realized. The response speed during rise time(time required for change of transmitted light intensity from 10% to 90%of the intensity at the time of applying electric field) was 250 μs, andthe response speed during fall time (time required for change of thetransmitted light intensity from 90% to 10% of the intensity at the timeof applying electric field) was 110 μs.

Further, even after removing electric field, residual birefringence wasnot observed.

Thus, in the case of the polymer/liquid crystal composite F-3P, twostates (a bright state and a dark state) were successfully realized byturning on/off electric field, and high speed response was successfullyrealized.

Example 4

Preparation of Liquid Crystal Composition

A nematic liquid crystal composition G-1 was prepared by mixingcompounds represented by the following formulae (q-1), (q-2), (q-3),(c), (e), (r), (a) and (b) in the weight ratio described below.Specifically, the composition was prepared by mixing: compounds (a) and(b) having the N-I point (clearing point) of 250° C. or higher, ascompounds corresponding to the component 1 represented by theabove-described formula (1); compound (r) having the K-I point of 46.1°C. and the clearing point (extrapolation value) of −3.6° C., as acompound corresponding to the component 2 represented by theabove-described formula (3); and other compounds (q-1) to (q-3), (c) and(e). Values shown at the right side of values of the weight ratio arephase transition temperatures of respective compounds.

(q-1) 5.0 wt % K 100.0 I

(q-2) 5.0 wt % K 97.5 N (90.4) I

(q-3) 5.0 wt % K 90.2 N 99.5 I

(c) 15.0 wt % K 40.6 N (33.1) I

(e) 20.0 wt % K 29.5 N 58.2 I

(r) 35.0 wt % K 46.1 I

(a) 7.5 wt % K 69.0 Sx 231.2 N >250 I

(b) 7.5 wt % K 69.0 Sx >250 N >250 I

Next, a liquid crystal composition G-2 containing the liquid crystalcomposition G-1 and the chiral dopants ISO-6OBA2 in the weight ratio of94/6 was obtained. Further, specifically, the liquid crystal compositionG-2 was held in a cell consisting of two ITO-glasses which was notsubjected to aligning treatment (cell thickness: 13 μm), and phasetransition temperature was measured using a polarization microscope.

TABLE 3 Liquid ISO-6OBA2 N* + I BP crystal concentration temperaturetemperature composition (wt %) Conditions Phase transition temperature(° C.) range (° C.) range (° C.) G-1 0.0 Lowering I − 76.2 − (N + I) −66.2 − N (10.0) temperature (1° C./min) Elevating N − 71.0 − (N + I) −79.1 − I temperature (1° C./min) G-2 6.0 Lowering temperature (1°C./min) Elevating N* − 52.0 − BP(X) − 60.5 − (BP(X) + I) − 66.0 − I7.5~14.0 temperature (1° C./min)

In the case of the liquid crystal composition G-1, the differencebetween the upper limit (76.2° C.) and the lower limit (66.2° C.) of atemperature allowing coexistence of the nematic phase (N) and thenon-liquid crystalline isotropic phase (I) (coexistence temperaturerange) in the lowered temperature process of −1° C./min was 10.0° C.Further, in the elevated temperature process of 1° C./min, the point oftransition from the nematic phase (N) to a phase in which the nematicphase coexists with the non-liquid crystalline isotropic phase was 71.0°C.

In the case of the liquid crystal composition G-2, in the elevatedtemperature process of 1° C./min, the following phase transition wasobserved: N*52.0 BP (or BPX) 60.5 BP (or BPX)+I 66.0 I. The differencebetween the upper limit (60.5 to 66.0° C.) and the lower limit (52.0°C.) of a temperature at which the optically isotropic liquid crystalphase is exhibited (BPX or BP temperature range) was 7.5 to 14.0° C.Thus, the liquid crystal composition G-2 exhibited the opticallyisotropic liquid crystal phase in the wide temperature range in theelevated temperature process.

A mixture in which the compounds (a) and (b) corresponding to thecomponent 1 were mixed in the same weight ratio as that in the liquidcrystal compositions G-1 and G-2 (compound (a):compound (b)=7.5:7.5) wasprepared. When the N-I point (clearing point) of the mixture (T₁) wasmeasured, it was 270° C. or more. Since the N-I point (clearing point)of the liquid crystal composition G-1 (Tx) was 71.0° C., (T₁−Tx) was199° C. or more. T₁−T×B in the case of the liquid crystal compositionG-2 was as follows:Liquid crystal composition G-2: T ₁ −T×B=270° C. or more−60.5° C.=209.5°C. or more.

Further, since the clear point of the compound (r) corresponding to thecomponent 2 is −3.6° C., T₂ of the liquid crystal composition F-3 is−3.6° C.

Since T₁ of the liquid crystal composition F-3 is 270° C. or more, theseliquid crystal compositions satisfy T₁>T₂.

Preparation of Mixture of Monomer and Liquid Crystal Material

As a mixture of the liquid crystal material and the monomer, 79.4 wt %of liquid crystal composition G-2, 10.0 wt % of dodecylacrylate, 10.0 wt% of 1,4-di(4-(6-(acryloyloxy)hexyloxy)benzoyloxy)-2-methylbenzene and0.6 wt % of 2,2′-dimethoxyphenylacetophenone (as a photopolymerizationinitiator) were mixed to prepare a liquid crystal composition G-2M.

Preparation of Polymer/Liquid Crystal Composite

The liquid crystal composition G-2M was held between a comb-likeelectrode substrate which was not subjected to alignment treatment andan opposed glass substrate (no electrode was provided thereto) (cellthickness: 14 μm), and the obtained cell was maintained in the state ofthe non-liquid crystalline isotropic phase at 45.0° C. In this state,ultraviolet (ultraviolet strength: 10 mWcm⁻² (365 nm)) was irradiatedfor 5 minutes to conduct polymerization reaction.

In the polymer/liquid crystal composite G-2P thus obtained, theoptically isotropic liquid crystal phase, in which diffracted light withtwo or more colors was not shown even if cooled to 25° C., wasmaintained. That is, the temperature range in which the opticallyisotropic phase is exhibited was further broadened compared to the caseof the liquid crystal composition G-2.

As shown in FIG. 2, as electrodes of the comb-like electrode substrate,an electrode 1 extending from the left side and an electrode 2 extendingfrom the right side alternate with each other. Therefore, when there isa potential difference between the electrode 1 and the electrode 2, thecomb-like electrode substrate as shown in FIG. 2 can provide a state inwhich two electric fields with different direction (upward and downward)are present.

A cell in which the polymer/liquid crystal composite G-3P obtained inExample 4 was held was set in the optical system shown in FIG. 3 tomeasure electrooptic characteristics. The aforementioned cell was set inthe optical system so that the incidence angle of laser light wasperpendicular to the cell surface and the line direction of thecomb-like electrode was 45° with respect to polarization plates ofPolarizer and Analyzer, respectively. When a rectangular wave having theamplitude of 100 V was applied, the transmission rate was saturated at ameasurement temperature of 35° C. At the time of applying voltage of 70V, the response speed during rise time (time required for change oftransmitted light intensity from 10% to 90% of the intensity at the timeof applying electric field) was 1 msec, and the response speed duringfall time (time required for change of the transmitted light intensityfrom 90% to 10% of the intensity at the time of applying electric field)was 0.7 msec.

Further, even after removing electric field, residual birefringence wasnot observed.

Thus, in the case of the polymer/liquid crystal composite G-2P, twostates (a bright state and a dark state) were successfully realized byturning on/off electric field, and high speed response was successfullyrealized.

INDUSTRIAL APPLICABILITY

Examples of applications of the present invention include a liquidcrystal material, a liquid crystal element using the liquid crystalmaterial and the like.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the disclosure has beenmade only by way of example, and that numerous changes in the conditionsand order of steps can be resorted to by those skilled in the artwithout departing from the spirit and scope of the invention.

1. A liquid crystal material contained in a polymer/liquid crystalcomposite comprising the liquid crystal material and a polymer for usein an element driven in a state of an optically isotropic liquid crystalphase, wherein the liquid crystal material exhibits the opticallyisotropic liquid crystal phase in the temperature range of approximately4.8° C. or more in the elevated temperature process but does not exhibita nematic phase.
 2. The liquid crystal material according to claim 1,wherein the liquid crystal material is a composition consistingessentially of a liquid crystal composition A, wherein the differencebetween the upper limit and the lower limit of a temperature allowingcoexistence of the nematic phase and a non-liquid crystalline isotropicphase or the difference between the upper limit and the lower limit of atemperature allowing coexistence of a chiral nematic phase and thenon-liquid crystalline isotropic phase is approximately 3.0° C. toapproximately 150° C., and wherein the optically isotropic liquidcrystal phase is not exhibited in the elevated temperature process, andchiral dopants.
 3. The liquid crystal material according to claim 1,wherein the liquid crystal material is a composition consistingessentially of a liquid crystal composition A, wherein the differencebetween the upper limit and the lower limit of a temperature allowingcoexistence of the nematic phase and a non-liquid crystalline isotropicphase or the difference between the upper limit and the lower limit of atemperature allowing coexistence of a chiral nematic phase and thenon-liquid crystalline isotropic phase is approximately 6.0° C. toapproximately 150° C., and wherein the optically isotropic liquidcrystal phase is not exhibited in the elevated temperature process, andchiral dopants.
 4. The liquid crystal material according to claim 1,wherein the liquid crystal material is the liquid crystal composition Bconsisting essentially of the liquid crystal composition A, which doesnot exhibit the optically isotropic liquid crystal phase in the elevatedtemperature process, and the chiral dopants, and wherein the liquidcrystal composition A comprises approximately 5 to approximately 80 wt %of component 1 having the clearing point T₁ and approximately 20 toapproximately 95 wt % of component 2 having the clearing point T₂, andthe clearing point T₁, the clearing point T₂ and the clearing point T×Bof the liquid crystal composition B satisfy the following conditions:T₁>T₂T ₁ −T×B≧100° C.
 5. The liquid crystal material according to claim 1,wherein the liquid crystal material is the liquid crystal composition Bconsisting essentially of the liquid crystal composition A, which doesnot exhibit the optically isotropic liquid crystal phase in the elevatedtemperature process, and the chiral dopants, and wherein the liquidcrystal composition A comprises approximately 5 to approximately 70 wt %of component 1 having the clearing point T₁ and approximately 30 toapproximately 95 wt % of component 2 having the clearing point T₂, andthe clearing point T₁, the clearing point T₂ and the clearing point T×Bof the liquid crystal composition B satisfy the following conditions:T₁>T₂T ₁ −T×B≧150° C.
 6. The liquid crystal material according to claim 1,wherein the liquid crystal material is the liquid crystal composition Bconsisting essentially of the liquid crystal composition A, which doesnot exhibit the optically isotropic liquid crystal phase in the elevatedtemperature process, and the chiral dopants, and wherein the liquidcrystal composition A comprises approximately 5 to approximately 70 wt %of component 1 having the clearing point T₁ and approximately 30 toapproximately 95 wt % of component 2 having the clearing point T₂, andthe clearing point T₁, the clearing point T₂ and the clearing point T×Bof the liquid crystal composition B satisfy the following conditions:T₁>T₂T ₁ −T×B≧200° C.
 7. The liquid crystal material according to claim 1,wherein the liquid crystal material is the liquid crystal composition Bconsisting essentially of the liquid crystal composition A, which doesnot exhibit the optically isotropic liquid crystal phase in the elevatedtemperature process, and the chiral dopants, and wherein the liquidcrystal composition A comprises approximately 5 to approximately 80 wt %of component 1 having the clearing point T₁ and approximately 20 toapproximately 95 wt % of component 2 having the clearing point T₂, andthe clearing point T₁, the clearing point T₂ and the clearing point T×aof a liquid crystal composition a, in which all the chiral dopants areexcluded from the liquid crystal composition A satisfy the followingconditions:T₁>T₂T ₁ −T×a≧100° C.
 8. The liquid crystal material according to claim 4,wherein the component 1 consists essentially of a liquid crystalcompound having the clearing point of approximately 150° C. or higherand the component 2 consists of a liquid crystal compound having theclearing point of approximately 47° C. or lower.
 9. The liquid crystalmaterial according to claim 4, wherein the component 1 consistsessentially of a compound represented by formula (1):

wherein: R¹ is hydrogen or alkyl having 1 to 20 carbon atoms, whereinany —CH₂— in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—,—CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl and an alkyl inwhich any —CH₂— is substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—,—CF═CF— or —C≡C— can be substituted with halogen; R² is hydrogen,halogen, —CN, —N═C═O, —N═C═S, —CF₃, —OCF₃ or alkyl having 1 to 20 carbonatoms, wherein any —CH₂— in the alkyl can be substituted with —O—, —S—,—COO—, —OCO—, —CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyland an alkyl in which any —CH₂— is substituted with —O—, —S—, —COO—,—OCO—, —CH═CH—, —CF═CF— or —C≡C— can be substituted with halogen, and—CH₃ in these alkyls can be substituted with —CN; A¹ to A⁵ are eachindependently an aromatic or nonaromatic 3- to 8-membered ring or acondensed ring having 9 or more carbon atoms, wherein: any hydrogen inthese rings can be substituted with halogen, alkyl having 1 to 3 carbonatoms or alkyl halide; —CH₂— in the rings can be substituted with —O—,—S—, or —NH—; —CH═ can be substituted with —N═; and A¹ to A⁵ are nottetrahydropyran rings; Z¹ to Z⁴ are each independently a single bond oralkylene having 1 to 8 carbon atoms, wherein any —CH₂— in the alkylenecan be substituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —N═N—,—CH═N—, —N═CH—, —N(O)═N—, —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C—, and anyhydrogen in the alkylene and an alkylene in which any —CH₂— issubstituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —N═N—, —CH═N—,—N═CH—, —N(O)═N—, —N═N(O)—, —CH═CH—, —CF═CF— or —C≡C— can be substitutedwith halogen; and n¹ to n³ are each independently 0 or 1; when R² ishydrogen or fluorine, n² and n³ are 1; when at least one of Z¹ to Z⁴ is—CF₂O—, n² and n³ are 1; when Z⁴ is —COO—, n² and n³ are 1; and onlywhen at least one of A⁴ and A⁵ is a condensed ring having 9 or morecarbon atoms, all of n¹ to n³ can be
 0. 10. The liquid crystal materialaccording to claim 9, wherein: R¹ is alkyl having 1 to 10 carbon atoms,wherein any —CH₂— in the alkyl can be substituted with —O—, —S—, —COO—,—OCO—, —CH═CH— or —C≡C—; R² is halogen, —CN, —N═C═O, —N═C═S, —CF₃, —OCF₃or alkyl having 1 to 20 carbon atoms, wherein any —CH₂— in the alkyl canbe substituted with —O—, —CH═CH— or —C≡C—, and any hydrogen in the alkyland an alkyl in which any —CH₂— is substituted with —O—, —CH═CH— or—C≡C— can be substituted with halogen, and —CH₃ in these alkyls can besubstituted with —CN; A¹ to A⁵ are each independently a benzene ring, anaphthalene ring or a cyclohexane ring, wherein any hydrogen in theserings can be substituted with halogen, alkyl having 1 to 3 carbon atomsor alkyl halide, and —CH₂— in the rings can be substituted with —O— or—S—, and —CH═ can be substituted with —N═; and Z¹ to Z⁴ are eachindependently a single bond or alkylene having 1 to 4 carbon atoms,wherein any —CH₂— in the alkylene can be substituted with —O—, —S—,—COO—, —OCO—, —CSO—, —OCS—, —CH═CH—, —CF═CF— or —C≡C—, and any hydrogenin the alkylene and an alkylene in which any —CH₂— is substituted with—O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —CH═CH—, —CF═CF— or —C≡C— can besubstituted with halogen.
 11. The liquid crystal material according toclaim 9, wherein: R¹ is alkyl having 1 to 10 carbon atoms, wherein any—CH₂— nonadjacent to the aromatic ring in the alkyl can be substitutedwith —CH═CH—, and any —CH₂— in the alkyl or alkenyl can be substitutedwith —O—; R² is fluorine, chlorine, —CN, —N═C═S or alkyl having 1 to 20carbon atoms, wherein any —CH₂— in the alkyl can be substituted with—O—, —CH═CH— or —C≡C—, and any hydrogen in the alkyl and an alkyl inwhich any —CH₂— is substituted with —O—, —CH═CH— or —C≡C— can besubstituted with halogen; A¹ to A⁵ are each independently a benzenering, a naphthalene ring or a cyclohexane ring, wherein any hydrogen inthe rings can be substituted with fluorine or chlorine, and —CH₂— can besubstituted with —O— or —S—, and —CH═ can be substituted with —N═; andZ¹ to Z⁴ are each independently a single bond, —CF₂O— or —C≡C—.
 12. Theliquid crystal material according to claim 9, wherein: R¹ is alkylhaving 1 to 10 carbon atoms, wherein any —CH₂— nonadjacent to thearomatic ring in the alkyl can be substituted with —CH═CH—, and any—CH₂— in the alkyl or alkenyl can be substituted with —O—; R² isfluorine, chlorine, —CN or alkyl having 1 to 10 carbon atoms, whereinany —CH₂— in the alkyl can be substituted with —O—, and any hydrogen inthe alkyl and an alkyl in which any —CH₂— is substituted with —O— can besubstituted with halogen; A¹ to A⁵ are each independently a benzenering, a dioxane ring or a cyclohexane ring, wherein any hydrogen in thebenzene ring can be substituted with fluorine or chlorine; Z¹ to Z⁴ areeach independently a single bond or —C≡C—; and n¹ is 1, and n² and n³are
 0. 13. The liquid crystal material according to claim 4, wherein thecomponent 2 consists essentially of a compound represented by formula(2):

wherein: R³ is hydrogen or alkyl having 1 to 20 carbon atoms, whereinany —CH₂— in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—,—CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkyl and an alkyl inwhich any —CH₂— is substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—,—CF═CF— or —C≡C— can be substituted with halogen; R⁴ is halogen, —CN,—N═C═O, —N═C═S, —CF₃, —OCF₃, —C≡C—CN, —C═C—CF₃ or —C≡C—CF₃; A⁶, A⁷ andA⁸ are each independently an aromatic or nonaromatic 3- to 8-memberedring or a condensed ring having 9 or more carbon atoms, wherein anyhydrogen in these rings can be substituted with halogen, alkyl having 1to 3 carbon atoms or alkyl halide; any —CH₂— in the rings can besubstituted with —O—, —S—, or —NH—; and —CH═ can be substituted with—N═; Z⁶ and Z⁷ are a single bond or alkylene having 1 to 8 carbon atoms,wherein any —CH₂— in the alkylene can be substituted with —O—, —S—,—COO—, —OCO—, —CSO—, —OCS—, —N═N—, —CH═N—, —N═CH—, —N(O)═N—, —N═N(O)—,—CH═CH—, —CF═CF— or —C≡C—, and any hydrogen in the alkylene and analkylene in which any —CH₂— is substituted with —O—, —S—, —COO—, —OCO—,—CSO—, —OCS—, —N═N—, —CH═N—, —N═CH—, —N(O)═N—, —N═N(O)—, —CH═CH—,—CF═CF— or —C≡C— can be substituted with halogen; and n⁶ and n⁷ are 0 or1, wherein both n⁶ and n⁷ are 1 only when at least one of Z⁶ and Z⁷ is—CF₂O—, and n⁶ and n⁷ are 0 when A⁷ or A⁸ is a condensed ring having 9or more carbon atoms.
 14. The liquid crystal material according to claim13, wherein: R³ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂—in the alkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH— or—C≡C—; R⁴ is halogen, —CN, —N═C═S, —CF₃, —C≡C—CN or —C≡C—CF₃; A⁶, A⁷ andA⁸ are each independently a benzene ring, a naphthalene ring or acyclohexane ring, wherein any hydrogen in these rings can be substitutedwith halogen; any —CH₂— in the rings can be substituted with —O— or —S—;and —CH═ can be substituted with —N═; and Z⁶ and Z⁷ are a single bond oralkylene having 1 to 4 carbon atoms, wherein any —CH₂— in the alkylenecan be substituted with —O—, —S—, —COO—, —OCO—, —CSO—, —OCS—, —CH═CH—,—CF═CF— or —C≡C—; and any hydrogen in the alkylene and an alkylene inwhich any —CH₂— is substituted with —O—, —S—, —COO—, —OCO—, —CSO—,—OCS—, —CH═CH—, —CF═CF— or —C≡C— can be substituted with halogen. 15.The liquid crystal material according to claim 13, wherein: R³ is alkylhaving 1 to 10 carbon atoms, wherein any —CH₂— nonadjacent to thearomatic ring in the alkyl can be substituted with —CH═CH—; R⁴ ishalogen, —CN, —N═C═S, —CF₃, —OCF₃, —C≡C—CN, —CH═CH—CF₃ or —C≡C—CF₃; A⁶,A⁷ and A⁸ are each independently a benzene ring, a naphthalene ring or acyclohexane ring, wherein any hydrogen in these rings can be substitutedwith fluorine or chlorine; any —CH₂— in these rings can be substitutedwith —O—; and —CH═ can be substituted with —N═; and Z⁶ and Z⁷ are eachindependently a single bond, —COO—, —CF₂O— or —C≡C—.
 16. The liquidcrystal material according to claim 13, wherein: R³ is alkyl having 1 to10 carbon atoms, wherein any —CH₂— nonadjacent to the aromatic ring inthe alkyl can be substituted with —CH═CH—; R⁴ is halogen or —CN; A⁷ andA⁸ are each independently a benzene ring, a dioxane ring or acyclohexane ring, wherein any hydrogen in the benzene ring can besubstituted with fluorine; Z⁷ is a single bond or —COO—; and n⁶ is 0 andn⁷ is 0 or
 1. 17. The liquid crystal material according to claim 4,wherein the component 2 consists essentially of a compound representedby formula (3):

wherein: R⁵ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂— inthe alkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—,—CF═CF— or —C≡C—; and any hydrogen in the alkyl can be substituted withhalogen; X^(a) is fluorine, chlorine, —CN, —N═C═S, —CF₃, —OCF₃, —C≡C—CN,—CH═CH—CF₃ or —C≡C—CF₃; Z¹² is a single bond, —COO—, —CF₂O— or —C≡C—;and L⁸ to L¹¹ are each independently hydrogen or fluorine.
 18. Theliquid crystal material according to claim 17, wherein: R⁵ is alkylhaving 1 to 10 carbon atoms, wherein any —CH₂— nonadjacent to thearomatic ring in the alkyl can be substituted with —CH═CH—; X^(a) isfluorine or —CN; Z¹² is —COO—; and L⁸ to L¹¹ are each independentlyhydrogen or fluorine, wherein at least two of them are fluorine.
 19. Theliquid crystal material according to claim 4, wherein the component 2consists essentially of a compound represented by formula (4):

wherein: R⁶ is alkyl having 1 to 10 carbon atoms, wherein any —CH₂— inthe alkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—,—CF═CF— or —C≡C—; and any hydrogen in the alkyl can be substituted withhalogen; X^(b) is fluorine, chlorine, —CF₃, —OCF₃, —C═C—CF₃ or —C≡C—CF₃;Z¹³ and Z¹⁴ are each independently a single bond or —CF₂O—, wherein atleast one of them is —CF₂O—; and L¹² to L¹⁷ are each independentlyhydrogen, fluorine or chlorine.
 20. The liquid crystal materialaccording to claim 19, wherein: R⁶ is alkyl having 1 to 10 carbon atoms,wherein any —CH₂— nonadjacent to the aromatic ring in the alkyl can besubstituted with —CH═CH—; X^(b) is fluorine, chlorine, —CF₃, —OCF₃ or—C═C—CF₃; Z¹³ is a single bond and Z¹⁴ is —CF₂O—; and L¹² to L¹⁷ areeach independently hydrogen or fluorine, wherein at least two of themare fluorine.
 21. The liquid crystal material according to claim 2,wherein the chiral dopants included in the liquid crystal materialcomprise one or more compounds represented by any one of the followingformulae (K1) to (K5):

wherein: each R^(K) is independently hydrogen, halogen, —CN, —N═C═O,—N═C═S or alkyl having 1 to 20 carbon atoms, wherein any —CH₂— in thealkyl can be substituted with —O—, —S—, —COO—, —OCO—, —CH═CH—, —CF═CF—or —C≡C—; and any hydrogen in the alkyl can be substituted with halogen;each A is independently an aromatic or nonaromatic 3- to 8-membered ringor a condensed ring having 9 or more carbon atoms, wherein any hydrogenin these rings can be substituted with halogen, alkyl having 1 to 3carbon atoms or haloalkyl; —CH₂— in the rings can be substituted with—O—, —S— or —NH—; and —CH═ can be substituted with —N═; each Z isindependently a single bond or alkylene having 1 to 8 carbon atoms,wherein any —CH₂— can be substituted with —O—, —S—, —COO—, —OCO—, —CSO—,—OCS—, —N═N—, —CH═N—, —N═CH—, —N(O)═N—, —N═N(O)—, —CH═CH—, —CF═CF— or—C≡C—; and any hydrogen can be substituted with halogen; X is a singlebond, —COO—, —OCO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or —CH₂CH₂—; and m is1 to
 4. 22. The liquid crystal material according to claim 2, whereinthe chiral dopants included in the liquid crystal material comprises oneor more compounds represented by any one of the following formulae(K2-1) to (K2-8) and (K5-1) to (K5-3):

wherein: each R^(K) is independently alkyl having 3 to 10 carbon atoms,wherein —CH₂— adjacent to the ring in the alkyl can be substituted with—O—; and any —CH₂— can be substituted with —CH═CH—.
 23. The liquidcrystal material according to claim 2, wherein the chiral dopants areincluded in an amount of approximately 1 to approximately 40 wt % perthe weight of the liquid crystal composition B.
 24. A mixture comprisingthe liquid crystal material according to claim 1 and a polymerizablemonomer.
 25. The mixture according to claim 24, wherein thepolymerizable monomer is a photopolymerizable monomer or athermopolymerizable monomer.
 26. A polymer/liquid crystal composite foruse in an element driven in a state of an optically isotropic liquidcrystal phase, obtained by polymerizing the mixture according to claim24.
 27. The polymer/liquid crystal composite according to claim 26,wherein the mixture is obtained by polymerization in a state of anoptically isotropic liquid crystal phase or an isotropic phase.
 28. Thepolymer/liquid crystal composite according to claim 27, wherein apolymer included in the polymer/liquid crystal composite has a mesogenicmoiety.
 29. The polymer/liquid crystal composite according to claim 26,wherein the polymer included in the polymer/liquid crystal composite hasa cross-linked structure.
 30. The polymer/liquid crystal compositeaccording to claim 26, comprising the liquid crystal material in anamount of approximately 60 to approximately 99 wt % and the polymer inan amount of approximately 1 to approximately 40 wt %.
 31. Thepolymer/liquid crystal composite according to claim 26, wherein thepitch is approximately 700 nm or lower.
 32. A liquid crystal element, inwhich an electrode is placed on one or both surfaces thereof, and whichhas a polymer/liquid crystal composite placed between substrates and anelectric field applying means for applying electric field on thepolymer/liquid crystal composite via the electrode, wherein thepolymer/liquid crystal composite is that according to claim
 26. 33. Aliquid crystal element, in which an electrode is placed on one or bothsurfaces thereof, and which has: a pair of substrates, at least one ofwhich is transparent; a polymer/liquid crystal composite placed betweenthe substrates; and polarization plates placed on the external sides ofthe substrates, and which has an electric field applying means forapplying electric field on the polymer/liquid crystal composite via theelectrode, wherein the polymer/liquid crystal composite is thepolymer/liquid crystal composite according to claim
 26. 34. The liquidcrystal element according to claim 32, wherein the electrode isconstituted on at least one of the pair of substrates so that electricfield can be applied in at least two directions.
 35. The liquid crystalelement according to claim 32, wherein the electrode is constituted onone or both of the pair of substrates placed in parallel with each otherso that electric field can be applied in at least two directions. 36.The liquid crystal element according to claim 32, wherein the electrodeis placed in a matrix state to constitute a pixel electrode; each pixelhas an active element; and the active element is a thin film transistor(TFT).